Now there are regulations that banks can't give students credit cards unless there is zero credit limit;

In addition, master students and doctoral students in subsidy income can get a card every month (any bank that has a cooperative relationship with the school can do it, which is what I do);

The credit line is X, which means you can borrow X yuan from the bank, as simple as that; If you spend Y yuan (Y is less than or equal to X), it means that you borrowed Y yuan, so you can only borrow x-y yuan, which means that your available quota becomes x-y yuan.