My friend is an indie game developer and he once told me the typical refund rate, which I think was only a little lower than this. I don't think the game length is playing that large a role here, rather people use that refund policy as a way to try out a game (like a demo). Probably most of the people who refunded wouldn't have bought it in the first place without that refund policy, so he shouldn't really view this as "because of this policy I lost 55K sales".