Those symbols indicate that the line has a 1/100 slope, high end to the right or left as the triangle indicates, I would guess that the whole line is sloped to that 6" by W17
aka,
WELCOME TO THE AWS WELDING FORUM!!
I would be more concerned about the fit up than the welding. From what I see I don't understand why there would be a concern with a 1% slope change. For welding? From the elevations shown it looks pretty flat. So, it is basically flat and has only a 1% slope. That isn't even enough under many circumstances to change the contour, mating surface of the fitting. Unless it is one awfully large fitting.
He Is In Control, Have a Great Day, Brent