I 100% agree with Jason on this one.
Too many parameters/factors contribute to that percentage number and for that reason it is only meant to be a guide, primarily when the clutch is new.
For example, if a seller mentions the clutch is new, then you should expect the wear to be under 10%. But once there's at least 10K miles on it, you'd need to assume the NCCP was set properly, the wear index stays at a reasonable number, there's no glazing, overheating, etc., etc., otherwise the wear ratio goes right out the window. In addition, the clutch friction material thickness varies a bit right out of the box, which further throws off those numbers. The NCR does a great job at calculating wear issues and spits that information back to the driver in the form of the 4-digit wear index on the scan tool. That number typically changes, however most people don't pay any attention to it. This is why many new owners are surprised when they see that they only ate up 5% wear in the first 10K miles but it now shows 50% at 20.
On top of all that, as soon as you figure things out, and you're convinced that you've got a solid 30K miles to go until your next clutch replacement, the damn release bearing will start leaking or your F1 sensor will fail, requiring you to tear it all down and start over any way!
In summary - quit worrying and enjoy!
Erik Di Somma
1989 228 (past)
1985 Quattroporte III (past)