I was told that numbers under two digits should be written out alphabetically (e.g. one, two, three, four, five, six, seven, eight, nine), and that anything two digits or over should be written out numerically (e.g. 10, 20, 100, 200, 1,400).
Is this best practice, and if so, how come? I feel that it looks better but I'm not quite sure why this is objectively better than writing them all out numerically (e.g. 1, 2, 3, 10, 20, 100 etc.)
Thanks