300 yuan money was deposited in the credit card of Agricultural Bank of China, and then the balance was checked. As a result, the available balance has increased by 300 yuan. At present, the balance has not changed, and I have never overdrawn. The current balance has not changed, because your overdraft limit itself has not changed. But why did the available credit limit increase by 300? It is because you have saved 300 yuan money that your current credit card balance has not changed, but the available credit limit has increased by 300. That available balance is the available credit card overdraft limit of your card itself, which has nothing to do with your 300 yuan deposit.