You may want to have predefined blocked slot reasons so staff can see why a slot has been blocked.
Navigate to the settings option, and select the 'Booking Form' wizard.
This setting is found on the 3rd tab 'Slots'.
Scroll down to 'When you want to block a slot and let your staff know the reason' and enter what options you want to enter for the reasons you blocked the slots. e.g "Reduced hours", "Reduced staffing". Note that customers will not see these messages.
Click Save at the bottom of the box.