1 : 15 RATIO and what is the range of ratios?

As indicated above, the variation from individual to individual is wide. And the number by itself isn’t good or bad. This isn’t like a lab test where there is a reference range and you’re okay within it and in trouble outside it. Your ratios are just your ratios; they correspond to the complex system that is your own unique physiology. Aside from that they have no particular meaning.

Mine are as follows:

Regular
AM 1:8
PM 1:11

Apidra or Novolog
AM 1:12
PM 1:16

The one part of your story that bothers me just a tad is this:

I, too, would like to know how he/she arrived at those numbers. Were they plucked out of the air? Lifted from some one-size-fits-all chart in a textbook? I know of no way to determine them safely and accurately other than through empirical testing; If there’s another method, I would be very grateful to learn what it is.