reduced winnings

I got a free spin bonus for a 25 dollar deposit i made.. I played the free spins half way thru my deposit.. I won 50 cents off of the 20 spins.. I then played for another couple of hours and took a break.. When coming back from the break i checked my bonus screen and it said no bonuses being used currently.. So I started to play again and hit for 1000$ so when I went to cash out they are saying I'm capped at 315 even though i didnt use the bonus money to play. Reason I thought that was because in the TnC it says that bonus money is only used when the players funds are exhausted.. I've ben a paying customer for a little under a year there and have spent thousands..