Detailed examples of Pen/Arm combat calculations

[Champagne]

The txt file that comes with the Armor Penetration Calculator states that the numeric values signifying the "Pen" factor will sometimes indeed fluctuate between one number and another, when the two different values are very close to one another at a given range. I just recently read this in the txt file and it impressed me greatly.

Is this was makes the AP Calc a "calculator"? I'm trying to understand why calling it a "chart" like a board wargame chart is less accurate than calling it a "calculator".

Thanks for the further info about the Armor Calculator. You explained its true function when I did not know.