The Quantity On Hand counts on item records are taken from all existing transactions - Inventory reports however show data as of a certain date. Therefore future-dated transactions can cause the two to not match.
Prior to entering a defect, it's important to check to see if there are any future dated transactions for the item. This can be done in a couple of different ways:
1. On the Item record > Related Records subtab, click on the "Date" column header to sort by date. Check to see if any posting transactions are dated after today's date
2. Run the Inventory Valuation or Physical Inventory report, and enter a date in the future - for example 12/31/2025