Once you become eligible in getting the Gratuity, it is quite simple calculation afterwards with any period of a year [the last in that company] wherein you have put up more than 6 months should be treated as one full year. In your case it has to be 6 years, no ifs no buts.
Thanks and Regards
Even,i have same case in my current organisation but they are ready to pay me 6 years service i have only 5 years and 6 months but LIC will be paid me 6 years service.
You have to request for your concern person for soft voice and get it done this matter.
Sr. Asst - HRA Dept.