The reason why: The Time for Schedules to Start is the time that the program reloads the schedules for a particular day. If these two occur at the same time, they will conflict and the schedule will never be executed.
For example, the current time is 2 PM and the schedule's first script is set for 4 PM. The Time for Schedules to Start should be something between these two times. The reason why: The calendar program loads the schedules for a particular day on the Start Time. If the Time for Schedules to Start is 1:30 PM (before the current time), the schedule will never load and thus will not execute at 4 PM as planned.