Sales Groups can be set in this screen. Enter a Group Description, and then a VAT Code can be set for reporting and accounting purposes (for explanation of the letters used see VAT), and the Payment Order is also set here. Sage information can also be entered - your accountant will be able to explain these to you. A deposit amount can be set for each sales group, which corresponds to the deposit button on the till. 

The purpose of this screen will become more clear as the other tabs in the Till Setup are used. See also Dispensing Fees and VAT