Scotweb design colors and accuracy?

[G_W]

So why is the threadcount and colour code information on their site for registering your tartan so precise?

Edited to add:

I understand that they are using best methods for matching their colors, I guess I was just wondering if the precision of the threadcount and and colour code information really helped. Here's a scenario. Say I order many yards of my custom tartan that I register. Then years later I want some more and, for some reason, I can't order it through Scotweb, but I can still use the information from the register and go through a mill. Will it help for that information to be precise? Or am I at the mercy of the mill?