Since there are 72 points to the inch, you'll need letters 720 points high.
You can enter any number from 1 to 1,638 (in half-point increments) in the
font size box and press Enter. You'll probably need to set paragraph line
spacing to 720 points or less to make the number fit on the page since most
fonts contain some built-in leading (line spacing) that makes the line
height greater than the nominal point size.