With a somewhat Average Academic Record, with a slight dip in Class 12th Marks, assuming youre from General Category, I believe you must target nowhere less than 99 Percentile, for chances to secure a Call for Interview from some of the IIMs as well as have great chances of Call from other Good MBA Institutes like Old IITs, MDI, IMT and many others. Besides CAT, you must also appear for other MBA Entrances like SNAP, MAT, XAT, NMAT as they too are gateways to some of the Top B Schools of India. However, with the kind of Academic Record you have, for a Call from Top 6 IIMs, you might just require a higher Percentile above 99.4-99.5. However, incase youve certain Categorical Advantage, you might require a lesser Percentile.

For more information and CAT Cutoff do follow the link below

https://bschool.careers360.com/articles/cat-cutoff