As far as I know, after you deposit, you can get more bonuses such as the double amount in your balance or something like that, you can get free spin or else, and you can play any games without limit except you lose your balance in that games. If you can win in some games, I think you can withdraw your money. But if you only want to chase to get a double amount in your balance, and you will withdraw all of the balance after you played, I don't think that the gambling website will allow you unless you play with the amount of money as you said.

I think that is fair because the site will not allow you to withdraw the money if you only play for one time then withdrawing the balance to get the double amount in your balance.