The configuration for schedule and booking start/end date is following below rules:

schedule period has to cover all bookings period.

For example, If there are two bookings in this schedule, one is from start date 01/01/2019 to end date 31/01/2019, another booking is from start date 01/05/2019 to end date 31/05/2019. then the start date of the schedule main tab has to be earlier or equal to 01/01/2019, the end date of main tab has to be later or equal to 31/05/2019.