What does 300 social security deduction mean?

Deduct 300 yuan from salary or income as social insurance expense.

Social insurance is a system organized and managed by the government, which aims to provide various benefits and guarantees for the insured, including medical care, pension and unemployment. Employers and employees are required to pay a certain percentage of social insurance premiums. These expenses are directly deducted from the salary and paid by the employer to the relevant institutions on behalf of the employees.