Discounts and promotions are defined in the Admin Portal and applied to a ticket at the POS.
The discount is added as a line on the ticket and the totals adjust immediately.
The list is filtered by what the Admin Portal allows for this ticket, this daypart and this staff member permission level. Check the Discounts and Promotions screen in the Admin Portal, and check the staff member job type permissions.
Source: Global Payments Genius POS User Guide. Newly built article, pending review.