Field help (ABAFORCE) 

This check box can only be selected if fixed execution times are indicated for a recurring task. It ensures that the execution request is created, even if if the time is exceeded at the moment when the batch server processes the recurring tasks for the day.

For instance, if a task is planned for 07:00, 10:00 and 15:00, but the batch server starts in the morning at 08:00: