I'm asking somewhat seriously here. I had to reschedule a regular appointment and I got this pop up.
It's not even self-consistent. First it seems to tell me that I can't do that this way, then it asks me if I want to do it.
How about put the question in the buttons:
Button 1 : Reschedule only this occurrence.
Button 2 : Reschedule all occurrences.
You shouldn't have to feel like you're retaking the "reading and comprehension" section of the SAT's to be able to answer a simple question.