Gratuity calculation remain same whether 58 years or 63 years.
for 12 years the gratuity amount is Rs.40,154 @basic Rs.5800/-
for 17 years the gratuity amount is Rs.72,332 @basic 7375/-
More the service period more gratuity amount.
Further for the purpose of gratuity calculation Basic+DA to be considered.
1st August 2019 From India, Madras