i think the wiki must be wrong put a link to that page so someone can correct it.
retarding the timing means making the points open later in the cycle or closer to TDC while advancing timing means making the points open earlier in the cycle before TDC. The points should always open before top dead center.
ie if the points are opening at 2mm before top dead center than they are more ADVANCED than if the were opening 1mm before top dead center.
to adjust the timing to more advanced you can make the gap wider or rotate the stator in the opposite direction the motor is spinning (on a puch e50 that would be clockwise). and vise versa for more retarded.
Now as far as those directions go, regarding timing for metra 80 kit, i wouldn't follow them since they have obviously been poorly translated and he directions that come with kits often are not correct due to the fact that kits are not always designed for the bike you are putting it on. Metra 80s are not designed for puch e50's, fyi.
I have heard that that kit likes a bit more retarded timing than usual. 2mm BTDC is a bit on the advanced side of the spectrum, but I could be wrong about what metra 80s like, I never ran one.
be careful tho timing that is too advanced will blow-up ur kit (even if it feels good), because it will bring more heat in to the cylinder, so watchout, and consult some metra 80 users.