It is totally hypothetical and shows what a few samples of 10 penis sizes that could "average" around 5-6 inches. Each column represents an hypothetical list of 10 penis sizes and the bottom row is each column averaged. It was not intended to be a scientific study in any way. It's just showing that if you took 10 guys off the street and checked their pants you possibly could find almost half packing some good wood and the others to be either just ok size or lacking size. Unless we actually looked at real data its kind of a guessing game. There aren't too many actual studies of penis size. I know there is the one of 15,000 males but don't really know much about it. I'm just guessing if I went into a gay bar filled with 100 men I would bet that at least a third of them would be over 7 inches and there would be at least 10 packing 8 or 9 inches. Disclaimer ( an opinion and not a scientific study!).
I know it's just an opinion but you gotta account for things that skew data. Suppose there are 75 more gay men that WOULD have gone to that bar but don't because they are ashamed of their "small" penis because they are "only" 5.5 inches. Those guys are now unable to be put in the total number of men in that bar and instead are replaced by only the guys more confident solely BECAUSE they know they have a large penis.
When I thought I was small I NEVER took a pic. I thought "why the fuck would I show off my little dick". Then when I actually took a pic for a potential partner, they basically said I am big. I took more, posted them and published them online to confirm. Now I am another guy flooding the internet with my big dick pics while another 10 guys who are average or small refuses because "there's no point". You never see them, but see all the hung gay men showing off online because they are big. Its a subtle bias that needs to be acknowledged before you draw conclusions.
The same thing with your chart of 10 men a gay man sleeps with (Because as the studies, which DO show the actual sizes sometimes, show if you pull 10 random men off the streets its more likely to look like [4.5, 5, 5, 5, 5, 5.5, 5.5, 6, 6.5, 7] which Average to 5.5) Of COURSE the bigger men are putting themselves out there so you find them. The "small"(and I put in quotes because they FEEL small because of porn and all the hung men yet are average) men may be shying away or regulating themselves as a bottom.
If you are a top you probably arent going to see many hung men because its almost expected for hung men to top and two tops rarely meet.
if you are a bottom you are probably going to see more big dicks because the hung men are sought after and therefore advertise more. The "small" men shying away as tops and therefore seen less.
Of course these are all PROBABILITIES and may not even happen but they must be accounted for before making conclusions!