Gratuity Contribution by employer is a part of the CTC of the Employee.
Legally there is not upper limit in Gratuity Amount. There are limits on the amount that will not be taxable as per the Income Tax Act (Currently Rs. 10 lakhs and likely to be increased to Rs. 20 lakhs soon).
The Company may decide to put a cap on the maximum Gratuity payable but it is recommended not to put any upper limit. Employee should get what is due.