You got 28 marks in AP PGECET and you are from ST category. For ST and SC candidates, there is no minimum qualifying marks in AP PGECET, so you have passed the exam and are eligible for counselling.

You can view colleges where your marks fit, check seat types, and see cut off information on Career360 here

https://engineering.careers360.com/articles/ap-pgecet-cutoff

This link will show you which colleges might give you admission based on your ST category score.