There are 2 ways to add multiple quantities of an item to a sale.

The first way is to use the number pad in the lower right of the POS screen.  To add 6 Long John's to the sale simply click the 6 and then the product name.

The other way to add a quantity of an item is to add the item to a sale and then click on the item in the Ticket Item Display area. Change the quantity using the numbers in the window and then click the X.  The quantity of items will change and display in the Ticket Item Display area.