Edited
Pardon me: Did you deposit 0.70 $ to your account?
Otherwise, who gave you the wrong impression that you received dollars? It may have been a license of 70 credits for use on this site, not more. (see T&Cs below)
Concerning your problem, please tell us how you came to know the amount
of 70 credits?
If this is noted as a payout in a leaderboard or if you received a mail, it should have been deposited in your account and should be visible in your account log (above the PLAY NOW button).
It also happens that people confuse credits and XPs. The latter don't have a value, they only contribute to your levels.They are included in one tab at the end of a game. See their number from the bar next to the level number.