Roman numerals were numbers for the Romans. To us they look like letters: IV, XXII, etc. And indeed they are, to the confusion of many students across the world.
It wasn’t until the invention of Arabic numerals that what we recognize as modern “numbers” came to be: 1, 2, 3, etc.
Still, it’s interesting to think about how these unrelated number systems are both related to the human hand. “I” and “1” both represent a single finger. Roman numerals has “V” for “5” (or a hand’s worth of fingers). And whereas the Romans used “X” for “10” (or the fingers of both hands) and the Arabic numerals only went to 9, there are still 10 of them if you count “0”.