First bookable day offset
These settings specify the earliest and latest possible day a booking can be made.
The First bookable day offset setting specifies the first possible day that can be booked.
Setting First bookable day offset to 0 will allow your customers to make same day bookings. If set to 1 then same day bookings would not be available but the following day could be booked (if its a bookable day). If set to 5 then the first bookable day will be today + 5 days.
Last bookable day offset
The Last bookable day offset specifies the last possible day that can be booked from the current day. It must be a higher value than the First bookable day offset.
Setting the First bookable day offset to 0 and the Last bookable day offset to 7 will result in the next week being bookable. Setting the First bookable day offset to 7 and the Last bookable day offset to 14 will result in the following week being bookable.
The bookable offset does not affect the notice period of a bookable period. The offset determines the first bookable day to be shown in the event booking question. How close to that bookable period when a booking can be made is determined by the notice period.