Hello ,

100 - your total percentile score is the percentage  of people ahead of you. 869010 are the number of candidates appeared for Jan exam. So rank formula is (100 - your total score) X 86901/100.

Your approximate rank will be :35,890.

Since you are SC you have chances of getting a category of rank less than 2,500 this is just an approximation. You will definitely get an NIT. If you are trying for advanced  start preparing from today and write well.If you are interested to write mains again ,write it. It might be a revision for your advanced. And if you get more than 95.87 percentile it will be good for you to choose the best NIT.