What does the double base of medical insurance payment mean?

Hello, dear, I'm glad to be answered by me. Insured units pay social insurance premiums based on the total wages of their own units last month and the monthly wages of individual employees above the base. If the total monthly salary of the employees of this unit is lower than the sum of the monthly payment wages of the employees, the sum of the monthly payment wages of the employees shall be the payment base. This is the so-called social security double base.