Kerning varies the type spacing depending on what letters are next to each other.
Does this help?
The machine size "was modeled after the 13-inch writing line. A design was selected to provide seven escapement values of 3 through 9 units with three unit, or pitch, sizes of 1/72, 1/84 and 1/96 in., in order to meet the design criteria."
I have a table with the data for each letter in the Times New Roman Font:
For instance: the "4" is 6 units, the "i" is 3 units. I could email you this technical print stuff to you if you want.