How to Calculate Payment for Skipping Notice Period When Salary Is Unpaid?

One of my friends has resigned from his position without serving the notice period, but he informed all the seniors and managers before leaving. He left on the same day he resigned. Now, he had already worked for 24 days before giving his resignation. The company is not willing to provide him with the relieving and experience letter; therefore, he is prepared to pay in lieu of the notice period, which was one month. Since he did not receive any salary for the 24 days he worked, how much would he need to pay the employer? His monthly salary was 13,000/-.

Thank you.

Management can deduct one month's salary. Let them process the full and final settlement where the employee will be paid for 20 days, and the deduction will be for 30 days. Therefore, whatever balance of 6 days remains, the employee should make the payment to receive the relieving letter.

Thank you.