From your message, it seems you have not completed either 11 full years or 10 years and more than 6 months to compute and consider it as 11 years. If a person worked in excess of 6 months, it is to be considered as one year and added to the full years of service.
Please be gracious to return the money without any demur. However, seek the old calculations if you have already signed an agreement between the company, gratuity trustees, and employee. Then, get a proper letter addressed to you informing you of the error in the calculation of a year, which, by virtue of being less than 6 months, should not be added but was erroneously included in the calculation as a year.
By acknowledging the letter to the company, demand from them the actual calculation that is entitled to you and your revised rectification of error and revised Final Settlement of Gratuity entitled to you Rs.0000000.00, less already paid on the date by cheque/transfer or other mode with the date of payment Rs.00000000000, the amount due or paid in excess. Then make a written demand for the refund of the excess amount to the company.
You need to check that all the calculations, except the number of years, are in order, and there is no circumventing the rules or attempts to make you pay back differently.
Official proof of the refund of the amount is absolutely necessary to be obtained by the gratuity treasurer. Normally, gratuity will be paid from the Gratuity Fund account and not from the company's official account. Therefore, care should be taken to get the Gratuity Fund account to confirm the return and refund of excess by you.
Sometimes when an employee resigns, they have to settle the gratuity from the Gratuity Fund. However, if the year has not ended to provide and transfer funds, and all the funds are invested as per criteria, there may be no liquidity in the Gratuity Fund Bank Account. Then either the company transfers the equal amount to the Fund account, thereby the Gratuity Fund settles the account directly, or the Gratuity Fund is worked out by the Gratuity Fund Trustees, and under their letterhead, they will work out the amount due to the employee. Then below the settlement of the amount due to the employee, the method by the company's bank account and full settlement is mentioned.
Every year, actuarial valuation is done by providing a long list of employees in the company. The details such as Date of Joining, present Salary/Wages, and Date of Birth of the Employee are provided to the Actuarial Valuer at the year-end. He prepares the list, and the provision required for each employee is mentioned, along with the total liability of the company as of that year-end.
Then the company deducts the amount in the Fund after the payout to the employees. Reconciliation is done as to Opening Balance, adding the amount received from the company. Total Rs. 000000 deduct amount settled to the employee by payment. The net fund amount is further reconciled by mentioning all the invested amount and accrued interest, interest received, and current bank balance. Then this is compared again with the Actuarial Valuer report. The shortfall is provided by the company and taken into account in the P/L & B/S.
Please do accordingly. Because there is always E.& O.E in everything, so it's better to settle the liability.