Think about this for a moment before you go read that post. Consider the numbers 24 and 50, written in Roman numerals:
24: XXIVFifty is, of course, a much larger number than twenty-four in the usual way we think about numbers' “sizes”. But notice that twenty-four is wider (on the screen) than fifty when written in Roman numerals. That's the observation that provoked the puzzle in the linked article.
Now go read it :)