I’m taking 5 AP classes this year and have decent grades in all of them except AP Calc. I have a D for my second semester grade, but my final grade, I predict, amounts to a flat C average. I don’t see many ways to get it up because there aren’t many grades going in this quarter. I’m pretty sure I don’t have senioritis either because I’m probably the only one working my butt off this quarter compared to other people in my grade who have worse grades.
As long as you are doing relatively well in your other classes, you should be fine. Your only con of getting an average grade in calc is that you will most likely have to take two classes through the math emporium (depending on your major, most people end up doing it), but that obviously doesn’t affect your admissions.
To answer your question, they look at your final grade. The transcript just shows your overall grade in each course. When you applied, though, they just saw the semester grade since that is the best information they had at the time. Now, if they see a drastic drop from your semester grades to your final grades, they might question. Notice, I said grades, as in plural. Like I said, one class won’t kill you. Good luck!