Predictors are all about predictions. Now if its exact then there is no need to add the word predictor. Every year students appear for examinations and they get admitted to colleges. The data those are collected from these past years are used to predict from the past year trends which colleges you can expect. The predictor may not give you the exact results then there are statistical fluctuations in pattern every year but it will give you some satisfactory which will hopefully coincide with your actual counselling results.

You can visit the link provided below for the college predictor:

https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer

I hope my answer helps. All the very best for your future endeavors!