i have sold a pair of converse trainers. They are size 9. Customer has emailed me saying that they are 8.5's not 9's. I am sure they are nines but I told her that she can return them for a refund. She got back to me stating that she would be happy to keep them if I knock £10 off. She paid £35 for them. Would you knock off the money or tell her to return them. If they are really a size too small why would you want to keep them