The Vendout option can be found on vending machines categorized as drink machines, excluding glassfronts.
By clicking a product to enter the machine Planogram page, you can set a machine selection to have a Vendout in the field seen below.
Vendout can be set to less than a selection's parlevel but more than 0 to show the selection's product as Sold Out once it reaches the indicated threshold. The Vendout quantity remaining is intended to keep a number of drinks still cold in the machine for when it is serviced and afterward a customer purchases the drink.