When you create a backup selection list, you can specify the priority for processing the jobs associated with the selection list.
See About priority and availability windows for selection lists.
You can also set a default availability window for selection lists. When you create a new selection list, the default availability window displays, but you must select the Limit availability to this daily time window option in order for the selection list to use the default window.
See Setting default priority and availability windows for all selection lists.