Sale return of Component of Fin Prod

Hi Xperts

I have a reqmnt.

I have sold a finished prod to a customer , e.g., 10 ink pens.During transportation ,  two pens' nip got broken.Customer did not return the full pens, however, they returned only the nips which i obviously a part of the pen.How to mapped this total Part-Return process in SAP.Plz suggest.

Rgds

Soumick