+1. Advance it past where the knife cut it loose, and then you can print past there.
I typically advance all new material out that far, simply because I don't know where the manufacturing hands' touched it last.
Exactly, the first part of the roll has been handled and finger printed, small dings, etc. Best to discard the outer part, I would bet, Oracal gives you that 18" for FREE, although I have never actually measured the 50 yd roll, I assume they give you a little extra.
Whenever I purchase roll good by the foot or yard, I am always given a little extra...