This may seem a little unrealistic to some but I really believe it has something to do with it. The NCAA takes their portion of the gate for all the NCAA Playoff games. So what UND does is reduces the number of people who attended the game and by stating that as the official number, that is what the NCAA takes from the gate. Therefore, if there was 1,000 more tickets sold than that, UND gets the profits from those tickets, without sharing.
Just one man's theory.