[Nyororin]

I think it`s more a mistake on the part of the poster. There is no indication that a bill said this. Most likely a major misreading of the water meter. They don`t start at 0, and are often completely arbitrary - just measured by the difference between one number and the previous.
Trust me, if they were using that much in less than a month - they`d be getting attention from somewhere.

Unless they have a bill that says their usage was that much, I wouldn`t even worry about it.