Hmmmm, I thought this one was a bit curly so I asked some people who know a lot more than my and here are two of the replies I got:
The vector programs that allow you to enter such stupid values - fake it (like Corel and Freehand). They don't really have that degree of accuracy.
-Paraphrased, Terri Pettit
and
Presumably that means "+/- 0.0001"
That means when you enter 0.0010, it had better output somewhere between 0.0009 and 0.0011. That's a joke, I hope. No leading zero... tee-hee.
+/- 0.0001 is crazy-overkill for things you're going to do with a drawing program. What, you're going to run 7-mil Mylar through your inkjet? Sheesh, it isn't a CAD program! In theory Illustrator is something like six decimal places, but I'm sure several calculations it does are not. Orders of magnitude... tee-hee.
You could guarantee +/- 0.0001 pixels in Photoshop, and that would probably work.
I used to do circuit boards; the cheap ones were +/- 0.005, and the good ones were +/- 0.002. There's so much creep when you add aditional processes (like step&repeat), that you want to minimize error at each step, so everyone tried to keep it all spot-on, but you would charge more to guarantee it. Still... Illustrator... 0.0001 It's a new cable TV show, right? Where's that hidden camera?
- r_harvey