The Solution to the Duae et Dimidia in Irenaeus?

[Secret Alias]

I love this forum because interacting with smarter people than me like Andrew Criddle. It stimulates my thinking like nothing else. I was on my walk a few minutes ago and some of my recent research was bouncing around and I starting thinking about the words in Irenaeus duae et dimidia:

Moreover, Jesus, which is a word belonging to the proper tongue of the Hebrews, contains, as the learned among them declare, two letters and a half, and signifies that Lord who contains heaven and earth; for Jesus in the ancient Hebrew language means "heaven," while again "earth" is expressed by the words sura usser. The word, therefore, which contains heaven and earth is just Jesus. Their explanation, then, of the Episemon is false, and their numerical calculation is also manifestly overthrown. For, in their own language, Soter is a Greek word of five letters; but, on the other hand, in the Hebrew tongue, Jesus contains only two letters and a half.

I always assumed that the "half" meant something like "half letter." In other words that Irenaeus thought there were full letters and half letters. But now, given my recent research I have another theory. If the nomen sacrum was ΙΣ and there was an overbar on top, the 'half' or dimidia was the overbar.

Why? Because I noticed in my research on the obelus that a straight line = division. https://en.wikipedia.org/wiki/Obelus I wonder whether the overbar = dimidia.

[Secret Alias]

Apparently in Greek mathematics "the numerator was written with an overbar, the denominator with the diacritical mark." https://www.math.tamu.edu/~dallen/histo ... count.html

[Secret Alias]

But was the overbar ever called a dimidia?