If its a traditional first deposit bonus, then its essentially a sort of rakeback. Like maybe every time you have generated 25$ in rake, this will release 10$ of your bonus. If you buy into a 2,2$ MTT, the rake is 0,24$, so after 100+ of those, you might get 10$ back as a released bonus. The best advice is to simply play the games, you want to play, and not think about the bonus.