The source seems very inaccurate. For one, it's almost impossible to project population that far in the future, but even then I think there's a lot that hasn't been taken into account. For example, birth rates are high in Africa right now but will probably decline eventually in the coming decades--this source seems to be based on projections if the birth rate doesn't decrease. And I'm not even sure if some of these places can support so many people. Niger is dirt-poor and most of its population lives on the edge of the Sahara--not ideal for agriculture or other resources. Egypt is already having water shortage problems, which will probably only increase with climate change. Also, the source has Nigeria's population dropping from 1.2 B to 700 M between 2200 and 2300.
This isn't to say this is a bad quiz, it's just that it's predicting the future is, more often than not, very inaccurate.
Yeah, I also agree with the source not being accurate, because it is virtually impossible the predict birth rates that far into the future. I just made this quiz with some statistics the video gave. On the 20 Most Populous Countries in 2300 quiz, I mentioned on the caveat that it won't be entirely accurate. I guess that I just forgot to mention it on this one, since I made the other one first.
This isn't to say this is a bad quiz, it's just that it's predicting the future is, more often than not, very inaccurate.
https://www.jetpunk.com/user-quizzes/1818355/countries-with-the-most-people-in-the-year-800000