Blake C: When does the Qty Invoiced number change on a Sales Order line item?
You'll need to wait for the sync engine to catch up on this one. First your sales order needs to get posted, then your invoice needs to get created and posted to QB. After syncing everything should be updated for you - I needed to wait for the invoice to be created and the invoice number to be retrieved from QB then my Invoiced Qty field updated. If you're not seeing your changes check QuickBooks > Resolve Conflicts and make sure you push a full sync.
~C