How rank determines admission?

I have 50 percentile in three years of high school and 20 percentile in the final year.
My GC will be sending all four years report.
So how will I be judged based on rank in Top notch colleges?

You’re a full need international student with an OK SAT but a questionable GPA – that’s not going to get you very far with the very selective colleges whatsoever. You should aim for colleges known to be generous with non-US applicants. Try searching in the international students’ forum.

Unless you attend a selectiv, academic secondary school (where not all students are admitted and where all are academically talented or college-ready) this rank means you should aim for universities and LACs ranked 50-150, plus regional universities.