Wager 20 times from your deposit bonus before you can withdraw it. If the wager min is too low, it will b easily abused by some multi accounts cheater. Since it's free, there should be at least some requirement like that
That is the best explanation on op question and I hope he/she still around to read this. That is why I do avoid bonuses, I should not have limit on my withdrawals.However if you know you can meet up with the conditions it is good you should takes the bonus as this will help you to make more betting or playing.