For any item there is a transaction history that should allow you to reconcile the in's and out's to come up with the current quantity on hand.

Just because you received 10 does not mean that you will have 10 on hand, you may have had a negative quantity of 10 when you received this item.

The easiest way to review this items transaction history is to print off the transaction history report. Look for anything thta might account for the error.