Dear Mahal,
The gratuity calculation depends upon your company's policy. Your company has already made a tie-up with LIC, and you have to calculate according to the guidelines of the policy.
The second method is according to The Payment of Gratuity Act 1972, i.e.,
Wage last drawn (Basic+DA)/26*15*number of years of service rendered by the employee.
The minimum service for the calculation of gratuity is 5 years, and it is not mandatory in cases of death.
In the above formula, 15 means 15 days. If the company is interested in giving beyond 15 days, that is their wish.