Do you intend to transfer your ticket to another person?

Officially you're not allowed to correct/change your age after booking of a ticket.

Unless you're availing any concessions(child/ Sr. citizen) TTEs will not bother much about your age so your age +/- 5 years is safe. Even 10 years difference will not create problems always.

Even if you're considered without ticket in low probability due to age issues, you'll be issued a new ticket and you'll need to pay ticket fare in full again but you'll be allowed to keep your berth and it'll not be passed to other passengers( RAC or Wait-listed).

→Always be humble & talk in soft tone with TTE when requesting to consider such issues in favor of you.

Unofficial way to change age

CRS( Chief Reservation Clerk) do have some discretionary powers and they can change it for you. But only if you go through some channel who knows CRS( relative, Railway employee or even a VIP link). Don't forget to carry your id & age proof in that case.