You should know that China has a large population, over 10 million population, there are 14 city.
There are 3 city 20000000. (does not contain the floating population.)
But that population is overweight in middle age people, with relatively few children, and most of those children are boys with relatively fewer girls since chinese parents keep killing off future potential mothers, so they can have a son. If you look at china's numbers for 0-15 year old girls who determine a population's future, the population does not seem as large as the overall figures you cite.