One burger for lunch is 660 gallons of water. So 27 is actually a very huge underestimation

This includes things like drinking, sanitation, etc. Derived the number from here: https://www.epa.gov/watersense/statistics-and-facts

Mostly lines up with this reference too, which focuses only on water usage at work: https://quench.culligan.com/blog/average-water-usage-per-per...

Since their example scales the water consumption with their electricity consumption one may conclude it was the fresh water consumed (evaporated) during production of the electricity. Gaseous H2O is an even more potent GHG than CO2.