Front: 16 digits (with intervals every four digits) are credit card numbers; Four digits directly below the card number, in which the validity period is separated by slashes (format: month/year); If it is a co-branded card, the number printed on the lower left is usually the member number of the cooperative merchant. Back: There are seven digits in the signature column, the first four digits are the last four digits of the card number, and the last three digits are the CVV security code. The back is also printed with the customer service hotline and the way to call the customer service hotline overseas. Card number, expiration date and CVV code are very important information, so don't disclose them easily. You can log in to CCB Credit Card-upper right corner-User Guide, with card introduction and user introduction.