Hello  ,For

Taking admission in IIM candidate should have to appear CAT MAT GMAT CMAT ,XAT like entrance tests. To Get top 5 IIMs in India candidate has to see your at least 99 percentile of marks in CAT MAT GMAT CMAT exams. Admission in in those top IIM that is IIM Ahmedabad, IIM Lucknow, IIM Bangalore, IIM Kozhikode, IIM Kolkata candidate must secure 99 percentile marks in Cat, MAT, GMAT, exam. The  entrance tests is taken for IIM admission in pgdm or MBA courses. Marks in the graduation, of 12th class examination, class 10 examination is not the basic criteria for taking admission in Indian Institute of Management. Only the marks from CAT GMAT mat CMAT  is the main criteria and the admission is done on the basis of merit only and personal interview.

some institutes like IIM Ahmedabad have some weight is an every year which can differs on 10 12th marks and on graduation marks as well.

you can go through this link below to Know more about that

https://bschool.careers360.com/exams/cat/amp

Hope this will help.