Extended Booking differs from Advanced Booking in that Extended Booking allows studio customers to book out a certain number of weeks past the current studio booking window.

For example, a three-week Extended Booking for a one-week current booking window allows Extended Booking Series holders to book classes for an entire month versus a single week.

This is enabled per Contract or Series so you can restrict this option to purchases of particular packages. Go to admin > scheduling/retail > series/contract and edit the contract you'd like to provide this option with.