Ah yes, that's it. My theme was aware of and compensating for the leading space, though I have no memory of it. At the time I coded it I probably assumed that the leading space was intentional and put there for a reason that was beyond the very limited knowledge I had then.
I also now remember seeing the note for 384c35418a in Code - Recent Activity, but it had already slipped my mind by last night when I observed the problem with the volume display in my status bar so I didn't make the connection.
And, of course, this all raises a question I have wondered about for a long time: Why is the Volume setting menu ordered with the quietest, lowest value negative numbers at the top and the loudest, largest value positive numbers at the bottom? Seems unintuitive to me, though I have fully gotten used to it by now.
Thanks yet again.