A stock error is whenever a count for a specific item increases from one inventory to the next, without an invoice to account for the increase. Another name for this is "negative consumption".
Consumption = (Beginning Count + Invoices) - Ending Count
This can also be attributed to a miscount from a previous inventory, or an error when adding an invoice.
When submitting your inventory, you will be notified of any potential stock errors.
Note - Don't worry about stock errors for individual areas, for example, "Main Bar". You should only be concerned with a stock error if it shows during the overall inventory review.
In the example above, the Molson Canadian could've:
Been counted incorrectly in the Previous Inventory
An invoice for this item was not added or was dated incorrectly
For the Pelee Island Shiraz Cabernet, it shows there was a delivery/invoice, but it is possible it was received as 1 unit instead of a case.
Having a stock error won't prevent you from submitting the inventory, but you should take steps to correct it before you submit, or immediately after the inventory.