Why did Tianjin Social Security only pay once in the personal account No.28?

Tianjin Social Security Personal Account No.28 is the only reason for payment:

Because the social security department generally checks the information with the cooperative bank in the middle of the month (around 15) and transfers the money to the personal social security card financial account, if you activate the personal social security card financial account before the check date, you can withdraw money from the card around the 28th of that month;

If it is activated after the check date, you can also withdraw money from the card around the 28th of next month. It can be activated at any time, and there will be a lot of money that has not been withdrawn in the month of activation and before.