Setting an item as unavailable (86'd) in Manager Console: edit the item in Merchandise - Modify Merchandise; click the check-box labelled 86'd on the Genral tab of the item and click OK to save. This prevents the FOH item button from being pressed and makes it black with red text as a visual cue that the item is out of stock.
Setting an item as a Count Down Item in Manager Console: edit the item in Merchandise - Modify Merchandise; click the check-box labelled Is Count Down Item and put the remaining quantity available for the item in the Qty. Avail field and click OK to save. This puts the available quantity of the item in parenthesis on the FOH item button and each time that item is ordered the availability count is decremented until it reaches zero, at which time the item button can no longer be pressed and makes it black with blue text as a visual cue that the item is temporarily out of stock.
Note: on the FOH Manager Menu there are options to 86 and un-86 items directly on a FOH terminal. There is also an Adjust Countdown Items option on the FOH Manager Menu where the quantity available can be adjusted or the item can be take off Count Down by pressing Clear.