Can I set up Over/Under delivery % to populate into the PO if I use category to purchase?

Hi All, 

The procurement and sourcing parameter has been set up to accept over and under delivery (screenshot 1).  When I place a PO using category, at the Line detail, the Delivery tab is not populated the over/under delivery of 5% (screenshot 2).  Where should I setup  to get the over/delivery populate into the PO if I purchase using category instead of item?  Thanks.