No idea how its being calculated but if it takes into account food lost during transport, tons of food spoil during transport in Brazil due to the terrible infrastructure for goods.
This number is coming from UN's Food Waste Index Report. Page 18 gives some explanation.
They measured the amount of trash classified as food and garden in Rio de Janeiro city.
This is counting cardboard, cans and plastics.
~42% comes from large generators, e.g. supermarkets, restaurants and schools.
I mean, China's per capita waste is similar to that of the United States or Germany, so presumably they throw roughly as much shit away per person as the US - it's just that, having four times The people, they naturally throw away four times The shit.