Field help (PTHQTYUOM) 

This field displays the received quantity in receipt unit. The quantity suggested by default corresponds to:

You can change the quantity as long as the receipt has not been created yet.
Once the receipt has been created, you can modify the quantity as well, but only for products which are not managed in stock. For products which are managed in stock, since the stock movements have already been performed, you are not authorized to modify the received quantity in this field: you need to use the Receipt modification function, available from the Actions icon on the receipt line.
Important notes on subcontract receipt lines with or without WO:

When a receipt line is partially invoiced (directly or through an order invoice), or when a line is linked to an additional invoice, you are no longer authorized to modify the quantity because this modification would impact the distribution of the invoicing elements.

When the receipt line originates from an inter-site or inter-company delivery line, you can:

SEEINFOIf the receipt comes from a delivery request and only part of the request is received, this request will be automatically split and the new generated request will or will not be closed depending on the closing value calculated for the receipt line.

When the receipt line is created from an order line (receipt of an order or shipment linked to an order line), you can: