Invoice dates are Showing different from actual in inventory

You had nothing on hand for that item when you created sales invoice 209 for 10 units. So there was no movement of inventory. When you purchased 120 units on 2/10/19, your backorder was filled.

Tracing exactly how the program allocated stock in your situation would be very difficult, because you apparently constantly run negative quantities on hand and then purchase enough to only partially fulfill outstanding sales invoices.