I saw a report a while back where a guy put 80L into 65L tank. That has to be more than a calibration mistake.
That's a deliberate and extremely low act from the service station....either that or the report was being a little loose with the truth.
But, yes I know what you mean, the B12 has a 20lt tank and I've put in 21lt and hadn't put on reserve...I had a little chat with the attendant and they agreed that it was probably wrong and kindly charged me for only 16lt, but that was in the country, not the city.