You are correct about that, maybe even in the upper limit. Given that you are aware of that, it makes even less sense to pretend that 1 billion people can keep

You are correct about that, maybe even in the upper limit. Given that you are aware of that, it makes even less sense to pretend that 1 billion people can keep eating the amounts of meat that are currently considered "normal" in the US. Some people can eat that much, or even more. Those people probably live in an environment where the land cannot produce that much vegetable calories that are eatable by humans, but do produce the low grade, cellulose rich stuff that was typically used to sustain cattle. In different geographies, where grain can be grown in big quantities, people would be better off eating the grain rather than feeding the grain to animals and then eating the animals. Meat can still be raised in that environment, as a complement, but probably not in the amounts we have gotten used to.