Do F-1 students making less than $500 need to file Minnesota tax return?

I am an international student on F-1 visa and lived in Minnesota from August till December only. I made less than $500 during that period working on campus. Do I need to file a MN Tax return for 2012? I lived in another state before where I did not make any money but was a full time student. I read in the instructions something about you don't have to file if you made less than $9000 so I wanna know if I need to file. Thanks