So based upon your information (BlackKnight89 and ProudofmyBoy), both your DSs were two of the 100 picked with Presidential Nominations to the USNA for the Class of 2020. That means that there are 98 Presidential Nominations slots left for the USNA. Those, who were not picked as the 100, will enter into a National Pool. Correct????
I think yes and no. I am a West Point FFR, so I am more familiar with what West Point does. I am assuming that USNA does the same thing.
The final charging of the nomination against an appointment happens in the Spring. So what West Point can initially appoints a candidate with any nomination. To meet the admissions goals, West Point will sometime switch nominations. So for Blacknight 89 or ProudofmyBoy DSs could be initially charged against 100 Presidential appointments, but if they have a candidate only with the Presidenital nomination that is #101, and someone appointed using Presidential nomination has another nomination, West Point will charge that candidate against the other nomination and free up a spot in the Presidential pool.
West Point's recommendation to MOCs are to nominate top 10 candidates per vacancy and don't have one nomination only policy. Nominating best qualified candidates regardless of other nomiations candidates might have will ensure only highly qualified candidates will be appointed. If a MOC has no double nomination policy, the top candidates in his or her district with other nominations (i.e. Senatorial or Presidential) will be excluded from getting the MOC nomination. So most qualified candidate in the Congressional district is likely to get a Senatorial nomination. However, the same candidate might not be competitive enough to win the Senatorial appointment. There can be only one. Sot another candidate in the district who was not good enough to get a Senatorial nomination will get the MOC nomination and win the Congressional appointment.