Maybe some of the experience Helms can comment/answer and better explain................... I think the race officer can call 1 or 2 boats that he identifies as over the start line, back. If there are too many boats making the task of identifying their numbers too difficult, then a general recall is called. After multiple false starts 'I' flag or 'Black flag' is enforced under stricter rules and zones,,,, I think ? I don't know.