The advance is built into the camshaft by Compcams already. Installing it straight up advances it 4 degrees.
You would need to degree it to actually see that.
Probably the most practical change would be to take 4 degrees out of it, so set it to -4 but I'm not sure that it is worth the effort?
I'd talk to Compcams about that first and see what they say. They may have a graph print out that will overlay between the two settings available but I suspect that you are taking some upper rpm's out of the engine that you might like to have?
It might or might not effect the idle as far as idle rpm? That depends on the engine itself, that's why you should talk to the tech adviser.