The penalty for a Ping An credit card that is overdue for 4 days is 130 yuan. The calculation of this fee may involve the following details:

1. Overdue time: According to the information provided in the question, being overdue for 4 days is considered a breach of contract and will incur liquidated damages.

2. Amount of liquidated damages: According to the information provided in the question, the liquidated damages for 4 days overdue is 130 yuan. The specific calculation method of liquidated damages may be stipulated by the credit card issuer.

3. Impact and consequences: In addition to liquidated damages, late repayment may also have a negative impact on personal credit records, which in turn affects future credit loans and credit card applications.

Summary: If a Ping An credit card is overdue for 4 days, you will need to pay a penalty of 130 yuan. Please note that overdue repayment may have a negative impact on your personal credit record.