"How is this data calculated? Averages are taken for all home games played by respective teams during the 2017-18 northern hemisphere season and 2017 Super Rugby season (these do not include friendlies or any knock-out fixtures). If no attendance figure was reported, then this game was ignored for the purpose of calculating home attendance averages. Population figures are taken from Wikipedia, as at 6th April 2018. City figures were used rather than greater urban areas. For Kings and Cheetahs, the average is calculated based on both Super Rugby and Pro14 fixtures.
According to Wiki today, Jo'sburg City population = 957,441, Urban population = 7,860,781, metropolitan population = 9,616,000
Equally, London comes in at 8,787,892; 9,787,426 & 14,040,163
To say that one of those is right, and the other 2 is wrong... is wrong. The stats from the OP were both explicit and (presumably - I can't be arsed to check) consistent, that you want to see different stats is on you, not the OP. Any misinterpretation is on you, not the OP.
Using any source for numbers to state the city sizes is problematic because local definitions and census data are not uniform, so we will have different definitions of what is included in that city population and what is not.
FTR, I don't know what your source is for Jo'sburg population of 4.4M (as opposed to the 1M, 7.9M or 9.6M) is, but the wiki article's source is the 2011 official census. Wiki is crowd sourced, but fully referenced, not just some local's estimate (though I fully agree that it often shows the bias of the author and cherry picking of data, that doesn't really appreciate!y to census information).
Again, if you have a better source than wiki, which is more accurate than official government data and census information from the nations involved, and consistent across different nations, then you can feel free to provide the stats you want. But to claim something is misleading when it isnt... is wrong.
What makes your figures right, and official government figures wrong? How would random fan #3,714 sitting Cardif know? Why would it be "wrong" to use the official figures instead of the ones you've provided?