Gratuity Calculation - company not giving me the calculation

My name is Ankit. I was working with the company for almost 8 years & after some time they had given me my Gratuity but they are not giving my calculation for the same. That time company was not giving us Salary slip. So I don't have any salary slip.
Now I got to know from some sources that they had given my less amount of Gratuity. Because LIC had release less fund & so they had to release less amount to me.
Recently I had asked for the calculation for my Gratuity ( How company had calculated Gratuity) & they are not giving me the calculation. They are simpling telling me thay your gratuity has been paid as per record.
Now how can I ask my remaining fund?

Dear Ankit,
You can calculate your gratuity with below given formula -
Last drawn basic / 26 *15 * no of years worked
Then you will be able to know the difference amount for which you can draft a letter and send it with registered AD for reply from the company. Also, in case you are not aware about your salary breakup then you can simply draft a formal letter and send it with registered AD and send it to the company. If company does not respond then you may send legal letter or approach labour office for further help. Also, if possible then you can draft email to the official email ID of your company and HR department to get the answer and which will be in result can act as proof of your followup with the organisation in the future.