For SS, IR dont have any separate quota, only discounted fare is applicable. For Male 60 or above 40% of base fare & for female 58 and above 50% of base fare provided as discount. Also mentioning age is not sufficient to get the discounts. You have to click in senior citizen box for each SS passenger asking for discount at the time of booking through IRCTC online portal. Also in PRS form you have to put a tick mark in the SS discount column to get the discount. Also this discounts are applicable against producing age proofs at the time of travelling to TTE.