Default Bin Allocation Quantity

Hello:

In SAP Business One 9.3, I noticed that the Bin Allocation Quantity would not "default into" the Goods Receipt PO, despite the fact that Item Master Data showed a Default Bin in the "Inventory Data" tab.

Why would Bin Allocation Quantity show a red 0, instead of the Quantity at the Default Bin for this line item in the Goods Receipt PO?
Thanks!

John