If your moc doesn't rank their list with a primary, then they are telling the academy admissions, YOU pick one. The academy MUST pick one. You only compete with who's on that list. NOT the national. Now; if you aren't the lucky winner of those 10 choices, then the remaining 9 nominees then go into the national pool.
Assuming you had more than 1 nomination, each nomination category is handled separately, and the same process for the other nomination. If you are admission's choice, good for you. If not, you and the others go to the national pool.
We actually have some individuals in our state with 5 nominations. "How pray tell is that possible". Easy. One of the senators and the representative each had 2 openings at the academy, so they submitted "2" slates. So we have some individuals with 2 nominations from the same rep; 2 from the same senator; and 1 from the other senator. And if they don't get one of those 5 slots, they will go into the national pool. And no; once you're in the national pool, it doesn't matter how many nominations you have. Multiple nominations only help increase the odds on getting a "Slated Appointment".