If that number is 0, you do not have any potions, and if it's above that, then it could appear on the item list with the number of how many (which will be stored in ITEM[3] anyways). Basically this will allow you to have an item for each element of the array (doesn't have to be 10 elements) but remember it starts with element 0, and ends with one less than the number in the DIM command.