In fact, the supplementary card you mentioned is not a supplementary card, but a debit card provided by the bank after you check the "automatic repayment" function on the credit card application form. Debit card is an ordinary bank savings card, but the credit card you applied for has an automatic repayment function, and you will automatically deduct money from the debit card after swiping the credit card. This is called automatic repayment. If necessary, the debit card can be activated online and used as an ordinary savings card.