Field help (SAUSRH) 

This is the unit in which the return is expressed. This information remains modifiable provided there have been no stock movements for the return line or provided the return line has not been the object of a credit memo.

During a direct return, the sales unit is initialized by the sales unit defined in the Product-customer record, if it exists. Otherwise, it is initialized with the sale unit of the product.
Entry of another unit is possible in a selection window. The units proposed are the sales units for the product previously mentioned, the packing units for the product and the packing units defined in the Product-customer record.

If the sales unit is modified, the Expected return quantity, the Return quantity and the conversion coefficient between the return unit and the stock unit are automatically recalculated in the new unit.

From this field it is possible to use the contextual button to: