According to the information you provided, the credit limit of Shanghai Pudong Development Bank Credit Card is 160,000 yuan, but the reason why you can only use 5,000 yuan may be due to the following aspects:

1. Bank restrictions: Banks may limit the use of credit cards based on factors such as the customer's credit status, repayment ability, and spending habits. This restriction is to prevent excessive consumption and the risk of arrears, and to protect the financial security of customers.

2. Credit limit management: In order to reduce risks, some banks will allocate credit lines to different consumption categories. For example, allocate part of the limit to daily consumption and part of the limit to large consumption. Limit spending amounts for different categories. Maybe you are currently using your daily consumption limit, so you can only use 5,000 yuan.

3. Optimal credit limit utilization: According to the principles of financial planning, it is recommended that the credit card usage limit should not exceed 30% of the total credit limit. Exceeding this ratio may have a negative impact on your credit history and credit score. Therefore, even if your credit limit is 160,000 yuan, you may only use 5,000 yuan each time within a reasonable range.

Of course, the specific reasons may require contacting the bank for further understanding and verification. If you have any questions about your credit limit, it is recommended that you consult the customer service or relevant staff of Shanghai Pudong Development Bank. Please note that the above answers are for reference only and may vary depending on bank policies and personal circumstances.