That's an overpayment. For example, it should have been returned to 800 yuan. If 900 yuan has been paid back, it will become-100 yuan.

Credit card balance, that is, the amount of consumption that has been generated.

For example, if the available amount is 10000 yuan and 1000 yuan is spent, then this 1000 yuan is the balance, and the remaining 9000 yuan is the available amount.

Deposit 1000 yuan, balance-1000 yuan, available line 1 1000 yuan.

Therefore, when the balance is positive, it needs to be repaid, and when it is negative, it means that there is overpayment and no repayment is needed.