You are not taking into consideration the people that live in cities, but not the "top 20" cities. I live in the Denver Metropolitan area. The area is rated 21st in population in US. With well over 2 million people, I would hardly consider this a "rural" area.
I did a recount, taking into account the 123 largest cities by population of China, given even the population of the suburbs, about to reach 450 million