0-2-X has been debated, misunderstand and very loosely interpreted since I've been around here. Below is from the introductory section guide to thorn-pattern and it jives with my conversations with Julian who is credited with discovering the 0-2-X pattern.


Guide to the Thoro-Pattern
Thoro-Pattern studies are broken out by age and time and using horses that have run at least six times – the three starts of the pattern (0-2-X etc.), plus at least three starts before that, in order to establish an effective previous top to compare to. Each of the last four – the three of the pattern, plus the one being measured – had to be within 42 days of the previous start, and all for the same trainer. The three runs in the pattern and the one being measured all had to be on the same surface (either dirt of turf), and either all sprints (less than a mile) or routes (a mile or more).
The numbers are compared to the “effective top” of the horse, which for the purposes of these studies was defined as the best figure the horse had run in the last 6 starts before the three race pattern began. If the horse runs better than that within the three race pattern, that figure becomes his effective top. Dirt patterns compared the race being studied to the horse’s dirt top, turf patterns to his grass top.

We do not make distinctions when we output the sheets. In other words, if a horse is coming off an 0-2-X, with the races six months apart, some grass and some dirt, we are printing the 0-2-X stats, even though they don’t really apply. We are doing this so you have something to work with, but it means you have to make distinctions. You can’t always take the results at face value for every horse – you have to handicap. Was there a significant trainer change that affected the pattern, or affects your opinion about what the horse will run today? An off race on a surface the horse doesn’t like last time out? Is the horse heavily raced, making improvement less likely than on average for the pattern?

The patterns shown are the ones for the surface today’s race is carded for, regardless of what surface the horse has been running on, and the effective top used will be the horse’s best number, regardless of surface or distance. The same categories apply as for the figure-based trainer studies – “top” means more than one point better than his previous effective top, “pair” means within a point either way of that effort, “off” means more than one point through four points worse than the effective top, and “X” means worse than that.