Small nitpick: an inch is 2.54 cm, not 2.56 cm. That makes the html element 284035.5 cm high, which I guess is the height of that "whws" div plus the height of text and margins above and below.
In any case about 28.4 m is a long way of from 18.94 km.
Although for css cm, browsers will use 37.8 px/cm instead of 96/2.54=37.7952 when making the conversion which gives the even 284000cm
The only way I can think of to get 18.94 km from the browser's interpreted 2.84 km is if the website is physically projected/printed on a 14.4 dpi display like a billboard
