E9 - Fixing wrong quanity on receiver (RcvDtl table)

I'm trying to fix a receiver mistake where 10 pieces were marked as received, but actual correct number should have been 4. The PO line was for 10, so not only is the quantity wrong, but the PO line is closed thinking it was received complete. We know that if an invoice has not been posted against the receipt, we can go to the receipt entry and make any changes required. However in this case, an invoice has already been posted. So, I created an updatable BAQ with the intent of modifying the VendorQty, POTransValue and ReceivedComplete fields, and the updatable BAQ would lead me to believe they can be modified, but I'm getting the following error when I actually run the BAQ against real data.

"Table: RcvDtl, Level:, Type: 3, RowID: 1, Text: Update of RcvDtl not allowed."

So my question, am I just doing the updatable BAQ wrong or can someone confirm this table cannot be updated.

Tim