The calculation method I listed is just one possible one among many. The basis idea is that you use pebbles. We know that the Romans used something along the li

The calculation method I listed is just one possible one among many. The basis idea is that you use pebbles. We know that the Romans used something along the lines of what I described, but it's very likely that many "numbers specialists" devised their own personal tweaks. For sure some people replaced a V with an IIIII. Some people replaced a III with a IIV. We know for a fact that 48 could be written as IIL. Etc. Maybe some people laid down their pebbles from left to right, some from right to left, some from bottom to top (like I did in my examples). So, yes, some of my calculations could be simplified. It's a matter of personal taste, and since Roman numerals were used for almost two thousands years, over a very large geographical area, it's almost certain that numerous local variation arose. But what is also almost certain is that TFA has zero grounds in reality. Roman people were not using Roman numerals to do their arithmetics. They were translating their numerals in a pebble setup, and performing their calculations using those pebbles, and then translating back to numerals.