I've always thought of "order of magnitude" as adding a zero, so anything less than 10 is a different order of magnitude.
Gets weird thinking about 9 being both one number less and one order of magnitude less than 10, while 99 is both 89 more and the same order of magnitude, but it's supposed to be a rough approximation.
Gets weird thinking about 9 being both one number less and one order of magnitude less than 10, while 99 is both 89 more and the same order of magnitude, but it's supposed to be a rough approximation.