Playersonly blackjack

I received a bonus offer from PlayersOnly for $10 to play casino games. I calculated that I would have to play 500 hands of BJ to earn the bonus at $1 per hand. I figured that I had a good chance for positive EV with the bonus. The rules were 8 deck shuffled after every hand, DAS, 3to2 BJ, no surrender. It didn't say if you could re-split but the opportunity never happened anyway. At the end of 500 hands I had a loss of $24, before the bonus was added. I don't know how to calculate the standard deviation for this so I can figure out how bad my luck was. If anyone can let me know I would appreciate it, and also if you could add the formula or link to somewhere where I can learn to calculate stuff like this, thanks.