In the event that your inventory count comes out wrong, consider checking the following.
When was track inventory enabled? If inventory tracking is EVER disabled, it will reset the inventory count. You can also disable the “Manage Inventory” permission to prevent users from accidentally disabling inventory tracking if desired.
If sales have not synced, it could be a temporary discrepancy. Check receipts. Are your sales syncing? If they are not syncing, this can cause your counts to be off until the next count can be made. Sales can also sync late if the POS wasn’t connected to the internet. If you do an inventory count while the POS did not sync, it can throw the count off.
Are all your stock receipts and inventory counts booked? If not, this can affect the end count. It is a good idea to ensure your stock receipts and inventory counts are booked before starting a new count.
Is your warehouse for the product in a different org unit than your POS? It is possible that the POS Terminal could be assigned to a warehouse that is different from the organizational unit. This can be changed at the point of sale screen inside the Sales tab in the back office. This issue can be caused by how the Organizational Units and terminals were set up at the beginning of inventory tracking.
Have you checked the Stock History Report? You can go to Evaluations > Stock History Report, or from the product list, you select this option from the top menu. This will show you a record of Inventory, Stock Receipts, and Sales for this product. This can help figure out where an error may have taken place.