@laurenofny - Yes, it’s likely that the admission folks at Penn will review your final transcript and not be pleased that you dropped the math class and you’re taking the Comp Sci class without a grade. Ultimately, however, my best guess is that you may receive a warning letter about this asking for an explanation, but no further action will be taken.
It would be a good idea to write to Penn now and provide an explanation of the change, IF you have a good reason for dropping the Calc class. For instance, one student I know in your shoes dropped a calc class because the regular teacher left and the long-term sub didn’t seem to understand the subject matter. Your situation may not be as clear-cut as this one, but if you can provide ANY reasonable explanation of the change, then telling Penn about it BEFORE they contact you would be worthwhile. (“I didn’t like the class” or “I didn’t like the teacher” do not count as reasonable explanations. If, however, you felt that the teacher was not just unlikable but also incompetent–like in the example I cited–it would be helpful to also provide corroboration of this from a school counselor. That’s what the student in my example did. He was far from the only kid in that class who dropped it, and his counselor wrote to his college to say so.)