How to report refunded Ebay transactions when filing as self-employed?

I sold a few  high-price items on Ebay last year, and now I'm having to file as self-employed (schedule C). Needless to say a 1099k form is being filed also, but it doesn't reflect the fact that about 30% of my transactions were refunded (the item was returned). I'm not able to find any place in income expenses to report these refunds. How should I approach this?