When he asks for m^2, he is comparing with his impression with Chinese houses, so it would be give a better comparison if the area is computed the Chinese way. In China, the area quoted by the building includes garage and unfinished basement (if any), and two level areas are added twice. Garage is about 40m^2, there is a two level area in this house as well. And bonus room may not be included in 3400ft^2.
So the total area is at least 350m^2 when computed in the Chinese way.