Field help (BPSNUMTRH) 

This field allows you to specify the supplier to which the purchase orders that you wish to select are attached. The choice of a supplier thus allows you to filter the selection panel with only the purchase orders placed with this supplier. If you have also entered a site, the selection panel is filtered with only the orders placed on this site with the specified provider. Once the first order has been thus selected, the supplier is no longer modifiable.
If you wish to save, for a container, orders placed with different suppliers, leave that field empty and use the Picking criteria to carry out your selection.