The marks for the class 12 is important in IIM because the marks for the class 12 contain some percentage in the IIM examination for the eligibility criteria so it's important to have the good percentage in class 12 I think so you have the good percentage but you can refer to the link below for the more information about the IIM eligibility criteria as and all staff I am providing the link below:

https://bschool.careers360.com/articles/iim-admission-criteria

I hope my answer helps. All the very best for your future endeavors!