As per SR Press Release(No. 825 /2018-19 dated 13.03.2019), the composition of Train No. 12633/12634 Chennai Egmore – Kanyakumari – Chennai Egmore Express and Train No. 12693/12694 Chennai Egmore – Tuticorin – Chennai Egmore Pearl City Express trains will be revised as detailed below"
First Class-cum-AC 2-tier – 1, AC 2-tier - 2, AC 3-tier– 3, Sleeper Class – 10, General Second Class- 3.
So there are only three 3A.