The article is pretty clear. The income distribution data in the image is extrapolated across the entire App Store.
"Before reading the rest of this post, bear in mind that these numbers are not necessarily accurate, and may not be representative of other categories in the App Store. However, if they were representative, the back of our napkin would give a very different split from the default assumed position:"
1% of apps (6,500) would be sharing 36% of revenue
($1.75bn), i.e. an average of $269,230 per app
19% of apps (123,500) would be sharing 61% of revenue
($3.05bn), i.e. an average of $24,696 per app
80% of apps (520,000) would be sharing 3% of revenue
($150m), i.e. an average of $288 per app