clearance clarification

[Bingo]

I'm back again with what im sure wont be my last question. The specs for this stove say that the flue connector with a single wall pipe must be 12 inches from a combustible surface. I was under the impression that a single wall pipe must be 18 inches from a combustible surface. am i reading something wrong, or do the stove specs override the 18 in clearance. Clarification would be much appreciated. This forum has been unbelievably helpful so far and i'm certainly grateful to have for all your expert advice.