Like I said before, a transformer has no impedance by itself, except for the resistance of the primary. You need to know what it is hooked up to on the secondaries, which one might assume is 47K ohms for a SUT. The resistance of the primary with no load, so far as I know, would typically be in the one ohm-ish range. I never measured a SUT, but I have measured the primary resistance of a few power transformers. Anyway, those numbers (3, 12, 27.5, and 48) are unlikely to represent the resistance across the primary. Maybe Intact would comment.
That's why I calculated the turns ratio based on the idea of the SUT hooked up to 47K ohms so that the cartridge sees 27.5 ohms. If you do the math, you get a turns ratio of 1:40-ish. I doubt that is correct. For vintage Japanese SUTs, I came to think that the ohms ratings are to guide the user to select a cartridge with internal resistance approximately the same as the ohm rating of the SUT. AudioNote seems to be using the numbers differently.