So I had a long phone conversation the other day with James Therrell, the brand manager for Cajun Line. (Frequent readers will understand why we had this conversation.)
He's a former nuclear engineer turned fishing-line geek and a really knowledgeable guy. In the course of talking, I learned something very interesting about knot strength and braid, often known as superline.
It seems the pound-test label on your spool of superline has little to do with the actual strength of the line. These lines are most often rated according to the strength of a palomar knot tied with a particular line brand and size.
Thirty-pound-test superline, then, means a palomar knot tied with that line should break at about 30 pounds. This, I've been told by a couple of people in the line business, is common practice among line companies. They just don't tell anybody.