The situation that your credit card is overdue for 5 days, with a limit of 20,000, and an interest of more than 400 may be due to the following reasons:

1. Overdue repayment results in interest: Overdue credit card repayment will Incur high interest charges. According to the information you provided, interest may be accumulated if the payment is overdue for 5 days.

2. The limit is exceeded: If your credit card limit is close to or exceeds 20,000, interest may accrue even if it is not overdue. Please pay attention to reasonable control of the credit card usage limit.

3. There may be other charges: In addition to overdue interest, there may be other charges, such as late payment fees, service fees, etc. Please check the bill or contact the card-issuing bank to learn the specific situation.

To sum up, here are some suggestions for your situation:

1. Pay off overdue balances as soon as possible: The sooner you pay off your debt, the less interest charges you will have. Try to avoid being overdue for a long time to avoid adding extra burden.

2. Contact the card-issuing bank for consultation: Communicate with the bank to understand the specific interest calculation method and other fee details, and seek their advice and help.

3. Properly plan financial budget: Ensure that there are sufficient funds for repayment in the future repayment cycle, and plan expenses and income reasonably.

Extended information:

After overdue repayment, banks usually calculate overdue interest at a certain interest rate. Specific interest rates and calculation methods may vary depending on bank policies. Timely repayment of overdue amounts is an important step in maintaining your personal credit history while avoiding additional overdue fees.