It seems the Magento quantity field corresponds to Quantity Available (Qty On Hand - Qty committed to orders) and not Quantity On Hand.
If we are updating inventory we are going to count how many we have of something and enter that number, but this would be wrong because there could already be orders in queue for that item or an order could be placed as we are updating the Qty. Is there a standard practice for dealing with this in Magento?
An example to clarify:
I have 13 of Product X in my warehouse. There is an order for 3 of Product X in queue to be shipped, so my Magento inventory would actually show a QTY of 10.
Now if 20 more of Product X come in from a supplier and need to be added to inventory, my stock people would need to see I had a QTY of 10, add 20 to that number and enter a new QTY of 30 into the system.
Between the time they open Product X's inventory tab, and they do the addition and click save, 1 more order for Product X could be placed. This would mean I would have 33 on hand, 4 committed to orders, QTY would say 30, but my quantity available for sale is actually only 29.