this is promotion described in the Mandarin casino page:
"Get 200% back on your money every 7 days at our casino!
Every Sunday for the first year of your account you will receive $40 worth of free spins at Mandarin Palace. All you need to do is make a minimum deposit of $20 on the day or ensure that you have done so in the 6 days leading up to that Sunday to qualify. Contact our support desk via Live Chat, telephone or email to have your Fortune Cookie Free Spins credited to your account."
I have regularly paid in the terms described and I received the bonus only the first week of "life" of my account. In the chat they told me that the promotion has expired and the promotions page needs to be updated. I believe it is not proper behavior and will avoid playing at this casino