Actually, you might have done better than 12.2 volts. I find that if I have been using my batteries and I check them with my voltmeter right after I have turned off a light or whatever, I get a lower reading than if I leave everything off for an hour or so, and then re-check. It's sort of like the battery needs to rest in order to give me an accurate reading. The difference can be pretty major -- I have seen it jump by two tenths of a volt. (I am not sure if this is true for everyone -- but I am sure it is true for my batteries.)
And here is why this glitch matters to me -- I try never to let my battery get below 12.1 volts. When it hits the magic number, it is time to run the generator (or to switch to my backup battery). But I find that I can go an extra day before recharging, if I wait an hour before checking voltage.