When you use "Change Items", you are selecting an item from the database 'Items' tab. You have to assign your icon graphic to one of the items in the database, or create a new item & assign the icon.
Also, if your 'operand' is "Variable 0001:atm", make sure that variable has a positive value. If it's 0, you'll be adding 0 items.
(check the variables setting with F9 in Playtest)
Be Well