Well, I learned a couple of things this evening about glasses.
One is, the OS and OD on the prescription stands for Oculus Sinister, or Left Eye, and Oculus Dexter, or Right Eye.
The two columns of numbers refer to corrections for refractive error and astigmatic refractic error.
And...apparently my vision, which I thought might have gotten a little better, is actually a little worse. Rats.
Looking at all this stuff because I'm going to try ordering a pair of sunglasses from one of those online services. We'll see how it goes.