Hii Rahul ...

As IISC ,Bangalore is one of the top college in our country , which admit only top rankers of some entrance exam.

As your marks is above 280 in jee main ..it is a good score to get admission in IISC , Bangalore .

And it is doesn't matter  that how many times you apply for jee main for admission in IISC ,Bengalore.If your rank is within cut-off,you will eligible for applying.

As per previous Cut-off for jee main:-

Gen.       :- .    295

SC .         :- .      225

OBC.           :-.   230

ST .             :- .   108

Hope it will help!!