When using a Shopping List, 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 Inventory Count.
The system pulls prior Inventory Counts to figure out how much of an item is used for every $1,000 in Sales. It then takes the most recent Inventory Count, looks to see how much there has been in Sales since that Inventory Count, and subtracts the Usage per $1,000 number from the most recent Inventory Count to theoretically calculate the 'On Hand' values.
To work successfully, the items need to appear on two inventory Counts which are dated a minimum of 45 days apart. This allows the system to get a good look at usage over a period of time to make that calculation.