I am a OIF and OEF veteren, i got diagnosed with UC right after my 3rd deployment from Iraq. The medical board eval was initiated before i even had a definitive diagnoses, then in under year later i was medically discharged with a 20% rating. The military wont give you a 30% or higher unless you are pretty screwed up, because if they do then you are offically medically retired and retain alot of benifits. Now if you get below that like me they will give you severance pay which is your base pay x2 x years served up to 12 max and wash their hands of you and you are now in the VA's hands. The VA found me 30% as a single guy i get 314 a month and the infinite headache of below average medical care with GI specailists which they are very short on it seems.
The process will go as such (well this is how it went for me)...
You get diagnosed the local medical board makes a decision on what to do with you ie discharge, retain, waiver...I can tell you right now if its chronic and non-deployable and you dont have many years in they will attempt dishcarge probably at 20%.
Next you can appeal this or accept it. Obviously appeal, which will take you to the formal medical board for AF thats in Texas, lackland. When you go to the med board you have to state your claim and case. What i mean is if you want to stay in then that needs to be expressed. Or if you want a higher percentage that needs to be said, but mind you, you can only ask for one thing and not both. You will have representation, VA or military either they suck...they will come up with their decision right there in like 10min. For me they left it the same 20% with severance pay.
Next you go back to your duty station and you have like 20 days to do a written appeal. Which you should do. As soon as you hear back from that its final, mine didnt change and like a month later i had my dishcarge orders. The end.
Although for more veterans out there that got medically discharged under 30% i read the pentagon is heading up a new medical board run by the Air Force to review all service veterans cases they think alot got short changed ecspecailly like the marines and stuff. You could get called back in for a another FMEB.