bonus balance ate my real balance

Was messing around with a new sportsbook promo, tossed some BTC in, grabbed a bonus, and thought I'd just clear the bonus and have fun. But now I’m noticing that as I play, my real balance seems to get drained before the bonus even gets touched. I always thought the bonus should be separate, so you burn through the bonus first, but maybe that's not really how these crypto casinos do it?

Is this normal for crypto casinos or am I just getting confused by the way they display the balances? I checked the terms and it's buried in there, but honestly, what’s the point of the bonus if it’s going to chew through what you actually deposited first? Any tricks for making sure you don’t lose your real balance before you even get to the bonus funds, or is this just the standard way these promos work now?