(2) Estimate based on 655 source lines for 4724 byte exposed class, with total 14682 class size
Apparently the first thing someone does after creating a language is to create a slider puzzle with it. The list chosen above is just those that were easy to find in a quick web search. This does not mean that other languages do not make slider puzzles, even great slider puzzles, but if it's not in this list it indicates that they were not easily found with a web search. I think this indicates that these languages are "the contenders" as chosen for the following slide.
As for the numbers. Interpret them as you wish.