OVERNIGHTS and EXTRA races
Every racetrack has a Condition Book in which the trainer points for that specific race. However, you cannot run a horse if you don’t have enough dance partners. So each and every racing day that the OVERNIGHT SHEET is released with the Entries for the upcoming race card, the Racing Secretary at each race track lists about a half dozen other races in addition to the Condition Book.
From all these races he selects those races with the most horses to fill his race card for the following day. So if you look at the entries for next Thursday on the Overnight Sheet that is readily available online for owners and trainers. Following the last race there are EXTRA races.