Prerelease allocations are unrelated to Promo Packs and Buy-a-Box promo allocations.
Wizards looks at a store's Tickets and Engaged Players to determine allocations for Promo Packs and the Buy-a-Box/Prerelease Early Sale Promotion.
Prerelease allocations—product allocated specifically for use at Prerelease events—are based on the attendance of your past two Prerelease events.