If the credit card is overdue for four days, the default penalty for a credit card worth RMB 10,000 is RMB 200.

Details:

1. According to the regulations of the China Banking Association, overdue credit card repayments will incur corresponding liquidated damages.

2. The calculation method of liquidated damages is usually determined based on the proportion of the overdue amount and the number of overdue days.

3. In this case, assume that the proportion of liquidated damages is two thousandths per day, that is, 0.02.

4. Four days overdue, the calculation formula for liquidated damages is: overdue amount × number of overdue days × liquidated penalty ratio = 10,000 yuan × 4 days × 0.02 = 200 yuan.

Summary:

Based on the above assumptions and calculations, if the credit card repayment is overdue for 10,000 yuan and is overdue for four days, you may need to pay a penalty of 200 yuan.

Extended information:

1. Different banks and different credit card products may have different calculation standards for liquidated damages. Please refer to the specific contract or relevant documents for reference.

2. In addition to liquidated damages, late repayment may also cause damage to credit records, affecting personal credit ratings and borrowing capabilities.

3. It is recommended to know the credit card repayment date in advance and make sure to repay it on time to avoid overdue fees and risks.

Note: The above answers are for reference only. The specific calculation of liquidated damages should be based on the actual contract or relevant documents.