Dear Aspirant,

Admission into IISC Bangalore is not by the JEE mains but through JEE advanced. You should clear the cutoff of JEE mains and then have to be in top 20 Percentile of your respective boards to be eligible for JEE advanced.

Once you have comply with the above criterias, you will be needing a minimum of 500 Rank in JEE advanced open category to get admission into IISC.

Hope this helps. Thank you.