Quick clarification on the nominations and appointments. About half of the class are filled with mandatory slots against a slate. Those slates are the moc's, presidential, numerous other military slates like Roth, Medal of Honor, disabled/deceased veteran, etc. the other half of the class is filled with those who received nominations but didn't get the appointment with the mandatory slots against a slate. E.g 10 nominees from a representative or senator. 1 gets the mandatory slot for the slate, the remaining 9 compete for the other half of the appointments to fill the class.
The presidential is just like the MOC slates, except it's a different number. I.e. To be on your MOC slate you have to be a constituent. To be on a presidential slate you have to be a qualifying brat. The MOC slate has a maximum of 10 nominees. The presidential slate has no limit. The MOC slate is guaranteed 1 appointee. The presidential is guaranteed a maximum of 100 appointments. The remaining 9 of the MOC slate compete nationally, along with the remaining 400,500,600, etc of the presidential and remaining of everyone else.
For what it's worth, for a brat to be eligible for a presidential, their parent has to be retired active duty military collecting retirement, or if still active duty, at least 8 years currently serving. No.... It doesn't count if your parent served 10 years and got out. It's current active duty with at least 8 years, or retired and collecting retirement benefits. Reserve military is also eligible, but it's based on points being they don't serve 24/7. So you can't count years.
As mentioned, there's also a number of other military related nominations. My suggestion is to click on the link in my signature block and look at the academy brochure. There's an entire section on all of the various nominations and the requirements.