This is based on your Student Loan Plan (which is based on the years you studied and on how much you earn now). A full overview can be found here: https://www.gov.uk/repaying-your-student-loan/which-repayment-plan-you-are-on

Student Loan Plan 1 (SLP1): If you were living in Northern Ireland or in Scotland when you started your course or if you were living in Wales or England and started your course before September 2012, you will have a Student Loan Plan 1. In this case, you will pay 9% of what you earn above the threshold, which is £19,895 for 2022/23;

Student Loan Plan 2 (SLP2): You will have the Student Loan Plan 2 if you were living in England or Wales when you started your course and if you started it after September 2012. In this case, you will be paying 6% of what you earn above the threshold, which is £27,295 for 2022/23