It's simple. It's just a ratio. Divide one by the other. 7 divided by 2 is 3.5 so the small one is doing 3.5X the large one. Or you can do it the other way. 2 divided by 7 is .286, so the big side is doing .286X the small one
I "still remember" that the old 440-6 (70 RR) was nearly 4:1 so at 5K engine RPM the alternator was doing about 20K. I don't know if "at the time" that was the original pulley or not. I tore up several alternators on that thing physically and mechanically and that led to electrically LOLOL
