Every one who is eligible receives one. The number of appointments charged to that nomination source is capped at a certain number. As you can see from the link below, USNA offers appointments to just 100 fully qualified candidates with a Presidential nom.
If 300 candidates are eligible for the Presidential, 300 will be given one. Only 100 of those will be offered an appointment; all must be fully qualified.
Navy and Marine Corps (Active & Reserve) page for Admissions at USNA.edu. Updated Fri Apr 19 04:59:18 EDT 2024.
www.usna.edu