According to the information provided, the repayment amount of credit card after 8 years overdue depends on interest rate, penalty interest and expenses. No specific interest rate, penalty interest or fees are mentioned, so the annual interest rate is assumed to be 20%.

1. Summary: credit card overdue for 8 years 1000 yuan.

2. Point by point explanation:

-Calculation of interest rate: Assuming the annual interest rate is 20%, 200 yuan's interest will be generated every year.

-Calculation of penalty interest: According to supplementary information, it is assumed that the penalty interest is 10% of the overdue amount, that is, a penalty interest of 100 yuan is generated every year.

-Costing: No additional cost is mentioned, so this factor is not considered.

-Total repayment amount: cumulative calculation of interest and penalty interest. After 8 years, the total repayment amount is (1000+8 * 200+8 *100) = 3,400 yuan.

3. Summary: After the credit card is overdue for 8 years, assuming the annual interest rate is 20% and the penalty interest is 10%, the repayment amount will increase to 3,400 yuan.

4. Extended information:

For more information about overdue repayment of credit cards, you can consult local banks or relevant financial institutions to obtain accurate rates and regulations.

Please note that the above answers are based on the information provided and assumptions, which may be different from the actual situation. The specific repayment amount may be affected by legal provisions, contract terms or other factors. It is recommended to consult local banks or financial institutions to obtain accurate repayment calculation and related information.