Field help (PNHCFMFLG) 

The return is validated has soon as you click Validate. Stock transactions are performed during the return note validation. The stock totals are updated and the stocks journal contains a log of the different transactions carried out.
The valuation of the return movements is made at the value of the original receipt (possibly adjusted) if the return is carried out from a receipt or at the stock value defined by the valuation method in the Product-site record if the return is a direct return (a withdrawal value can be used in this case if the valuation method allows a zero value stock return).