After talking to Fang and learning more about Black Whirlwind's past in the arena you are able to talk to Gambler Daoshen about the favor he mentions earlier in the game. Because you can now get into the back room of the arena, Gambler Daoshen asks you to go talk to Sweet Poison Lyn about upping the money limit to his gambling game.
By talking to Gambler Daoshen he asks if you would take his payment to Sweet Poison Lyn for him. The interaction with Sweet Poison Lyn takes a few moments and she sends one of her contacts to tell Daoshen that she received his payment. You can also by gems from her if you wish. You can choose to either take his money or pay yourself but he will pay you back in full plus a gem if you choose to pay with your money or you can tell him to keep it. The bets can now be made higher if you wish to play his game.