Hard to say. If he had 2 slots, which is possible in any given year, he could nominate up to 20 people. Most MOCs try to nominate as many as possible. If only 15 met the MOC's qualifications, it's possible that he/she only nominated 15 instead of 20.
I've also heard that some MOCs will nominate the max 10 for one spot and tell other that they are "contingents" in case one or more of the 10 aren't qualified. However, the others don't have noms unless one of the "original" 10 aren't qualified (e.g., medically).
It could be either of the above situations.