As I have recently done some experiments and recorded the settings, I thought I would post the findings.
Good experimentation - thanks.
What I'm interested in is 1-point font size changes in the 23 to 27 range, where they start skipping sizes. I also use left margin 2 and right margin 1, neither of which seems to be accessible from the slider.
I think perhaps I'm maligning the coder, while the values may well have been made by some marketing of management person with limited technical understanding, like many product managers I've known. If so, please accept my apologies, programmer.