Class 12 percentage marks needed for US universities (namely UIUC)

I got admitted into UIUC and I was wondering what my minimum class 12 percentage should be so that my admission is not rescinded. I emailed them and they said that it should be similar to class 10 marks. I got a perfect CGPA in class 10, but I don’t expect more than maybe 75% in class 12 - I was slightly sick and could not concentrate at all. Could my admission be rescinded?

@IamINTP Any idea about this?