Stem and leaf displays

In The Visual Display of Quantitative Information, a stem-and-leaf plot is shown of volcanoe heights (page 46 in the 2nd edition).

I can’t figure out why the digits on the right hand side of the chart aren’t sorted. It seems like sorting this would make it easier to see how many volcanoes are 7,800 or taller, rather than just how many volcanoes are in the 7,000-7,900 foot range.

Is this chart example just not optimal, or am I missing something?

thanks…mike