The main card is relative to the supplementary card. The main card is the main account of the account. It has the highest usage rights and has certain control rights over the supplementary cards. The supplementary card is an account that has no independence of its own. It uses the same card account as the main card. When the supplementary card is newly opened, it has the same payment permissions as the main card. The main cardholder can use the same card account as the main card according to actual needs. Control payment channels and payment limits for supplementary cards.