This is the British and American counting method. Because there is no unit of "ten thousand" in English, we use "ten thousand", that is, the "ten thousand" in English is ten thousand, so this comma is put in thousands of miles. There is no single word for "1 million" in Chinese, but "100" is added before "10,000" (there are also 100,000 and 10 million, both of which are preceded by numbers), while "1 million" in English has a special word, that is, millions, so millions are marked with commas. That is, according to their habits.