Who has the bigger middle class - China or the US?

By one measure, China:

The Big Picture: China by the Numbers

• Shanghai boasts 4,000 skyscrapers -- double the number in New York City. Still, 17% of the entire Chinese population lives on $1 a day. Only about 300 million people in China, or 23% of the population, are considered middle-class.

Since the population of America is less than 300 million, and at least 25% is in poverty or tenuous circumstances, China has now a much larger "middle class" than America. I suspect in absolute terms the average member of the American middle class has much more money than the Chinese equivalent, but this transition is remarkable. America is very far from ready for China.

By the way, the word "only" in the above quote is kind of weird. What's "only" about 23% of China?