All the more staggering because back in those times the majority of the world population resided in China and India. At around 0 A.D, there were 100M people in India and 58M people in China[1][2], leaving a few tens of millions in the rest of the world.
By the way, in the 202BC battle of Gaixia, 250,000 people died in a world of 150M people[3].