A turnover requirement obliges you to use promotional credit a set number of times before withdrawing. It began as a defence against abuse and now shapes what an offer is worth.
If a service gave out credit that could be withdrawn immediately, people would sign up, take it and leave, and criminals would use the accounts to move money. Requiring the credit to be used first makes both unprofitable.
As a multiple. A 20x requirement on a credit of 500 means 10,000 must be staked or spent before a withdrawal is allowed.
The platform keeps a running total against the target and usually shows progress in the account. Many also keep promotional funds in a separate balance from cash, with rules about which is spent first.
The requirement, more than the headline amount, decides what an offer is worth. A plain-language walk-through for Chinese readers is this Traditional Chinese post on how activity turnover is calculated, written from a player's notes (娛樂城活動流水怎麼算). Its central point holds everywhere: the large print attracts, the small print decides.
Multiply the credit by the requirement. If the resulting figure is more than you would ever spend on the service, treat the credit as worth nothing.