A number of stock holding figures are automatically maintained by the Herschel:

Stock On Shelf

The quantity of the partnumber that is currently in stock.

Stock On Order

The quantity currently outstanding on works or purchase orders.

Stock Reserved

The quantity reserved to satisfy works or sales order requirements.

Stock Available

The stock on shelf quantity minus the stock reserved. This is how many could be taken from stock without “stealing” from a works or sales order reservation.

It's important your staff understand what the different figures are, especially the stock available figure.