The top half of bands that make finals go in the last half of the performance slots during finals, and vice versa. The rule was put in place because Hebron performed near the end of semis in Grand Nats, won semis, then had to go first in finals, which ultimately negatively impacted their score. The following year (or it might’ve been last year, I can’t remember), BOA put in the so-called “Hebron rule.”
EDIT: Of course someone beat me to it.