Why would my rating get denied and then increased for the same condition?

Thank you Mose!! Think we're on the same page. Hope you're listening Manny. VA Reg'l will print everything they have but if he has a NSO from one of the Veterans Associations chartered by Congress to rep Vets in claims, they can guide him and smooth the path.

He should check. But putting it on this site is asking for opinions, answers, explanations and experiences.

That's exactly what I repeatedly recommended he do. But, facts are facts (i.e., consult your NSO, letter of disagreement within one year of decision, private attorneys are not necessary when you have an NSO, etc. are not opinions, they are facts). One of the purposes of "RallyPoint" is to provide guidance and help based on knowledge for our sister and brother Veterans. I don't hold back what I know from the last 4 decades; and I'm still active in the VA. You know what to do Manny. Go do it and just stay on track with your NSO.

Being "...one of the few...", more of us have a single condition than you realize, and it DOES NOT HAVE TO BE a combined disability for Total and Permanent. What you refer to as "Individual Unemployability" is called "Total and Permanent Unemployability" by the VA. I deal with Total and Permanent and Total and Permanent Unemployability Veterans regularly in my groups. Total and Permanent invokes a different set of standards than Total and Permanent Unemployability. "Total and Permanent" you may work, for one. Ratings are not just combined (added together), they are based on mathematical table cross referencing your highest rating with your next highest rating, etc. (available from the VA or any NSO office). So, no matter how many 70% ratings you have the table never goes over 99.9% on the bottom line; which really doesn't matter since any time you go over the 5% line you go to the next highest even percentage (for instance, if your rating is 64% on that table you are 60%, if it's 65% you go to 70%). By the way, you can have an additional rating on a single event less than 10% (i.e., 2%, etc.). So, if you run the numbers on that chart and you come up with 64% but your getting paid at the 70% rate rather than the 60% rate, that's why.
FOLKS, SEE YOUR NSO FROM YOUR CLAIM REPRESENTATIVE, DAV, AMER LGN, VFW, PARALYZED VETERANS, ETC.

SSgt Greg Willard - A combined disability rating means the rating for all your rated conditions, which could be for a single disabling condition if that is the only disabling illness or injury or the totality of disabling conditions - but that is what they use for determining eligibility. I realize the ratings standards are different for being rated Total and Permanent, and for Individual Unemployability, which is why I spelled out the standards for Individual Unemployability. I didn't address the rules for Individual Unemployability explicitly, however, since I stated that one of the qualifying factors is you be unable to work it is implicit in the standards you don't work while receiving the benefits. And the term Individual Unemployability is the VA's term (see https://www.va.gov/disability/eligibility/special-claims/unemployability/). I try to use the same terminology whenever possible to avoid confusion and make it easy for people to look up further information.
And actually, COMBINED is the term the VA uses because that is the process you describe - they are not simply added, they are combined. (For example, they take the highest rated disability first, so if you have a condition rated at 50% disabling, you are 50% 'able', so if the next rated condition is also 50%, you are not 100% disable, you are 75% disabled because they took 50% off the 50% 'ability' you still possessed, then you are 25% 'able' and they continue to decrease that by the percentage of each rated condition, which is how the combined rating table works).
As a former medical WTU 1SG and Army Health Center SGM I counseled many Soldiers going through the MEB/VA rating process, and continue to assist Soldiers who are filing either initially or to have their disability determinations upgraded. I agree with you, and encourage all Soldiers to contact their NSO (National Service Officer) or VSO (Veteran Service Officer) to assist with their claims, however check with fellow Veterans to see which ones in their area have been most thorough in reviewing medical records with them to identify all potential claims, following up on documentation requests, providing complete information with references to applicable regulations and DOD instructions and the VASRD so the Soldier, Sailor, Airman, or Marine can look it up themselves, etc.
They should also describe in detail the process for evaluations and use of the VASRD, so the rated individual knows what to expect, particularly for the psychological exam if the Soldier, Sailor, Airman, or Marine has PTSD or TBI. Being asked some of the questions about the traumatic event without being forewarned can be triggering. Having someone who is familiar with the entire process to guide them is invaluable, particularly for those with PTSD, TBI, mental illness, or taking medication which affects higher cognitive function. We send our Battle Buddies, Shipmates, Wingmen, and fellow Marines off to do battle with a bureaucracy and the very problems for which they are being rated often cause them issues (forgetting appointments or facts while being examined, getting upset and not cooperating fully, getting frustrated and giving up) in getting an accurate rating. They need our assistance.

Preaching to the choir on PTSD, etc. We have the busiest VAH in America in Tampa (appts).
Made the methodology clear. Can not get to 100% by simply adding the ratings. After that we're playing semantics, re-explaining each other, and wasting our Veterans appt times. Mine are lined up so I'm sure yours are too.
Readers see benefits.va.gov/compensation/rates
Scroll to Table 1-Combined Ratings Table. Note that the max is 99% (which automatically goes to 100%). Just because I may have a 100% for a single condition doesn't mean the 10% for tinnitus, 30% for musculoskeletal, 10% for hearing loss, etc., etc. that I may have, disappear; they are still part of your disability records (as I'm sure SGM Johnson will confirm).
I'm shortchanging my Veterans on their allotted time, and after 4 decades I don't want that reputation. I'm 10-7 on this SGM.

FINAL: VETS, GO STRAIGHT TO YOUR NSO/VSO. Keep in mind State/County Service Officers do NOT represent you, they are very knowledgeable, fantastic individuals that assist you in preparing the paperwork and forward to one of those organizations chartered to represent you.