Earned/privileged leave can be encashed in FNF statement by the employer. You may refer to the Factory act, appointment letter issued to you, standing orders, and employee rule book/HR policy and leave rules of the company. Employer should keep the policies within knowledge of the employee. If you paid leave to your credit employer can not deny the encashment.
You may not give acceptance on the copy of the FNF statement or you may record your reservations/protest on FNF statement to be returned to company and retain a copy. You may raise a query in writing under acknowledgment to the good offices of your appointing authority, MD, Company Secretary with a copy to Head-HR, and request for a written reply.
As you had submitted notice of resignation your date of retirement was known to employer, hence on its own employer should have paid the gratuity to you in FNF settlement. You may include demand for payment of gratuity in your representation for paid leave and submit form I under acknowledgment and submit a copy of Form I under acknowledgment to controlling authority for Gratuity which may be ALC in your case.
You may go thru SE act applicable to your state.
As you had submitted notice of resignation, and if the employer accepted it before effective date of resignation, you can agitate term it illegal and demand notice pay as described in your appointment letter. The immediate acceptance might have rendered you jobless and without any source of livelihood. You may approach a competent and experienced service lawyer at your location with all records. Your lawyer may help you to structure your representations and/or may prefer to issue a legal notice.