It's the "Drilling jets" article, and it should be under the performance tuning category linked on the front page (and if not there, under one of the tutorials pages). I don't know how accurate that chart is though, and they're right that it doesn't have a lot of information on it. I seem to remember hearing that the Dellorto jets are measured in something non-arbitrary (like a unit of measurement ... go figure) but I've never heard anyone give an answer for how the Bing jets are measured (or at least nothing that any of us could measure).