Then I noticed that, just a little bit off from where I'd turned it, there was a small blue pointy sticker. And so I thought, "Aha, I know what this means," and turned it to that point, and indeed a moment later the water was at the perfect temperature.
This makes me very happy.
Crossposted from Dreamwidth (original here), with comments. Comment here or there; comments here will eventually be duplicated to there.