Occasionally the stock figures held in the Store module may become inaccurate, ususually because of problems such as power cuts, hardware failures or users not logging out of Herschel correctly.
The Manager module's verify stock figures option will scan your stock file and ensure that the current stock on shelf, stock reserved, stock available and stock on order figures are consistent. It also checks the actual sales quantities on your plan:
Sometimes, if you know your stock figures are totally inaccurate, it may be quicker to simply zero the stock figures for a range of items. You can do this using the Manager module option zero stock figures: