The ESV says that “the number of mounted troops was twice ten thousand times ten thousand,” thus, 200,000,000 men. That is, of course, more than John could count, and so he vouches for the accuracy of the number with the words, “I heard their number,” meaning that the Lord told him. Yet, as with so much else in the book of Revelation, we are not to take this number literally. In point of fact, the word that John uses here is “myriad,” a term that does not designate “10,000” so much as “innumerable.” Furthermore, he writes literally that there are “twice myriads of myriads,” roughly comparable to the English expression “zillions.”
16 The number of mounted troops was twice ten thousand times ten thousand; I heard their number.