Rework order for FG return from customer

Hi Experts,

Please help me in following scenario :

I have made delivery & Invoice for sales order for quantity 800 unit. Out of that customer returned 600 unit bcoz of poor quality.

I made return order & did post GR to rework storage location.This stock is return stock in MMBE. Now I have to process on same FG and bring its to unrest.use stock. How to map this in PP

Regards.