Admission is done on the basis of cutoff based on your rank(which depends on your marks) in jee advanced.

The cutooff for year 2018 had opening rank 35 and closing rank 122.

The parameters considered while deciding the JEE Advanced 2019 IIT Guwahati cutoff:

1. Total no of students
2. Previous year cutoff
3. Total number of seats available
4. Difficulty level of the exam

With this you can get an idea of your chances for admission in iit guwahati.

Hope this helped.