Smitty Two wrote:

As for this being a computer-generated problem, you would think
that any code that transforms "47" into "87" would have been
caught long ago.

Be that as it may, how do you account for the first unusually high
reading, a bit more than a year ago IIRC? Seems like any erroneous
reading or transcription thereof would get spotted / corrected /
credited the next month.

Yes, I do recall another similar high reading a year ago that I'm going
to look into in the next few days.

I expect that it would have been corrected for the next billing cycle,
as this one would have.