<human>: Can you condense the text into three sentences or less?

I just remembered something I thought I'd share. In my third year in college, I was taking some difficult classes. I'm one of those people who loves to calculate my grade when I should be studying, so I did this often. When I got my grades back, I was shocked - there was no way I earned a 2.67. I asked all my professors what my grades on the final exams were, plugged that into the formulas, and realized that TWO out of THREE gave me a lower grade than they should've. My grades were corrected and I ended up with a 3.23 that quarter, which is about what I expected. And then, I was horrified. I was almost in my final year of school and realized that for three years, I had just accepted my grades without question. Professors are human, with hundreds of students to evaluate even when they're tired and want to get done so they can enjoy their breaks. I wish I had verified all my grades in all my classes from the start.
<bot>: Professors are probably messing up your grades once in a while, wish I had thought of it in the first place.