It's funny actually, this is something I learned from grade school! One of my elementary school teachers made this rule in class to write out numbers from [one

It's funny actually, this is something I learned from grade school! One of my elementary school teachers made this rule in class to write out numbers from [one to ten] and then use numbers to represent everything greater than ten [11, 12, ...]. Helped remove a lot of confusion then as to when is it OK to use numbers vs. writing-them-out!