They refund 0, they just keep the coins.
No offense, but are you fucking kidding me?
I personally put out 500 coins to cover coiniums losses. The pool op, Raistlinthewiz, put up THREE THOUSAND FIVE HUNDRED CAT of his own personal stash to cover overpaid coins. What does that mean? It means he paid out legitimate coins on mining that was done on invalid coins. Those coins never existed, but were paid out anyways. So, other invalid coins were caught before they were paid out, so yes, you didn't get paid out, but those coins never existed to begin with. Try to consider that everybody got screwed by these forks, ESPECIALLY Coinium.