Inventory management is a big deal. You need to store it in properly, monitor lot/batch expiration dates, and be able to find it when you need it! A big part of finding it is keeping an accurate count.
When you count your inventory once or twice a year, each count takes lots of time, usually done in a hurry, sometimes with outsourced help and may reveal significant gaps comparing to the books. Frequent counts of parts of your inventory (cycle counts) is more efficient and improves overall accuracy.