A green-white-checkered is an overtime restart used when a caution falls near the end of a race, restarting the field under green so the race finishes with a lap run at speed instead of under caution.
Even the lap count is not settled. DIRTcar’s Super DIRTcar Series and the American Sprint Car Series both write that “all races must be completed in a ‘green-white-checker’ finish,” meaning a caution before the leader takes the checkered sends the field back to a restart to “run for two consecutive laps before completion” — with officials free to allow a one-lap “white-checkered” finish instead. Florence Speedway gives exactly one try: “if a caution occurs, the race will be given one chance at a ‘green-white-checkered’ finish. If another caution comes out, the race will be considered completed at that point.” Florence runs a clock over the top of it too, a one-minute-per-lap time limit on every regular show event from the initial green.
How many attempts your track allows decides whether a late caution is a chance to win or the end of your race, so learn the rule before you are sitting third with two to go.