One of my fill ups yesterday, 200.5 on the trip, range 3, 20.25 litres, temperature c16C. (Staines)
The other was 205.2 on the trip, range 7, 19.90 litres temperature c22C (Wachtebeke otherwise known as somewhere in Belgium)
So you've definitely got more than 19 litres in there, and the fuel is coming from an underground tank so temperature at delivery isn't going to vary much. As for pump accuracy, I don't doubt there a few out there where they are erring on the profitable side of the tolerances, but I have filled up in so many garages from so many companies in different countries I think I have flattened out the rogue ones.