Okay so the article is wrong about some points. We have evidence for both IIII and IV notation in classic roman archeological finds. The obvious example is the entrance fee doors around the colliseum in Rome, they're are engraved with numbers, in both forms of notation.
Seriously I figured they used abacus for everything they just figured out the notation to write it down in at the end some would convert to the if notation while others would not.
It seems the subtractive notation was used for engravings, where keeping it short was important and nobody was going to do calculations with the numbers anyway.
> Seriously I figured they used abacus for everything they just figured out the notation to write it down in at the end some would convert to the if notation while others would not.
Yes, this is exactly right, and should be at the top of this discussion thread. Romans (like the Greeks, the Babylonians, and others in the ancient world) did their calculations using a counting board. Roman numerals were only used for recording the final answers.
Seriously I figured they used abacus for everything they just figured out the notation to write it down in at the end some would convert to the if notation while others would not.