Holy Moly, I was about to post that when the Garmin Edge 530 that I ordered yesterday arrives, I'd have to go through the menus and see what my options are with regards to zeros and recording, but I went to track the package and found it was already sitting on my front doorstep. It's plugged in right now to top off the battery.

I'm not made of money, and buying two new cycling toys within a week is out of character for me in some ways. I think it's a subconscious coping mechanism for taking my mind off the end of the world. Anyhow, to celebrate the fact that I'm still alive and, as yet, uninfected, I'll go out this afternoon, pair the Edge 530 with the power meter, and take it for its maiden spin.

I do appreciate all the comments in this thread. The different power readings were unexpected to me. The explanation for that was a real mystery to me at first, though now it seems perfectly understandable. It just took some figuring out, and I appreciate the comments here helping me do that.