accounted0 on "Summer Program Eligibility"

I have an odd question: how do the Big 4 classify freshmen through juniors for their summer programs (not the internship for rising seniors)? By credits earned or by years away from graduation? I ask because I accumulated a large number of credits from another major before I switched to accounting. However, I'm only in my first year of accounting classes. I still have two and a half years of college ahead of me and all of my upper division accounting classes left to take.

Thanks!