You can’t withdraw bonus cash credits that you’ve received as a special casino offer. They are not real money and are usually transferred to a separate ‘wallet’ (Bonus wallet) not to get mixed with real money deposits and other winnings. All the bonus credits (and winnings from Free Spins) are subject to playing through: wagering a determined amount ( = wagering coefficient x the number of credits) before the withdrawal, complying with minimum and maximum withdrawal limits, and a bonus expiration date.