My supplier's annotations are "estimated" and "actual", which seems a more useful thing to track (so your estimation algorithm can recalibrate itself when it sees an 'actual' reading and not for the results of its own estimations.)

Oh yes, I think it tracks actual guesses as well. It's just that real readings are also distinguished into by-employee and by-householder.

I suspect, however, that they do that distinction by treating everything brought back by a person in a van as by-employee, irrespective of whether the person in the van saw the meter or just saw a card left in the window.