When you make a bitcoin transaction, there is always an extra bit leftover that goes back into your wallet. In this case, that extra bit happened to be large, due to the way the "coins" in the wallet were arranged.
So what will happen with these 90+ leftover BTC? They weren't added back into the pool balance
h2o has been keeping his 3% cut in the same wallet since the beginning -- at this point that cut is around ~200 BTC, corresponding to the 5000+ BTC paid out. The 90 BTC belongs rightfully to him.