Gary,
the ajustments will move your powerband up or down a bit.
If you retard the cam timing it will give you more top end,
If you advance the cam, it will give you more bottom end.
In general you would run the cam straight up at 0*. The marks are also usefull to DEGREE the cam in. There is good info on how to do this at crane cams or comp cams website.
Perry.
PS- Ford retarded all the smog 460 engines 8* from the factory to reduce emmissions, so if you had a smog engine and just replaced thetiming set with a performance set, you would gain major power.