Quite not sure about how much they hold and also actual data on how much bitfinex had hold during the attack is still unknown and also no any exact amount that got stolen is given out. Price is moving in uncertainty and lots of panic created in traders including me. This over night hack event has also make me lost significant in value but not direct lost of bitcoin because i haven't any in bitfinex.
It couldn't have been as much as every thinks because the price is on the rebound right now and is continue to increase towards what it was before the hack attack happened yesterday.