An Extra is an item or a service that you can add to your booking contracts. This can be ex: equipment, staff, housekeeping, catering, etc.
The basic prices and the quantities can be changed manually by contract.
Goo under RENTALS > EXTRAS.
Enter the NAME, the default PRICE and the TAXES application.
You can also linked your LEDGER CODES, if you created some under ACCOUNT > ACCOUNTING.
In the EXTRAS sub-tab, you will be able at any time to create new ones, edit and archived them.
Note that the changes will not affect the contracts already created, regardless of their state.