When creating a Shopping List through Purchasing Assistant, the 'On Hand' amount may appear to be calculated incorrectly due to the fact that it displays a '0' for one or more items. It is important to keep in mind that the 'On Hand' field is calculated based on historical usage, so it does not pull the most recent Stock Count.
The system pulls your prior Stock Counts to figure out how much of an item is used for every $1,000 in Sales. It then takes your most recent stock count, looks to see how much you have in Sales since that stock count, and subtracts the Usage per $1,000 number from the most recent Stock Count to theoretically calculate your 'On Hand' values.
To work successfully, the items need to appear on two Stock Counts which are dated a minimum of 45 days apart. This allows the system to get a good look at your usage over a period of time to make that calculation.