Hi Toshita. 

I will tell you that you can safely sit on 280 marks and guarantee your seat in any of these two college. Though the previous year cutoff for ST category is lower than what I have preacribed but you never know when the cutoff will boom upwards and it is always safe to be on higher marks than required so work well and score around the prescribed marks and surely you will get into these colleges. 

Hopefully my answer will help. 

It will come maynot be in first round but in corresponding rounds it will come.