There are three electrical jumpers on the circuit board. Jumper "A1" controls the whole ignition timing curve, normal or advanced, which has the most affect at low RPM.  Jumpers "B" control the amount of curve to the timing without changing the low rpm timing, which have the most affect at high RPM.

Below you can see the graph for the A jumper and the two resultant timing curves resulting from whether the jumper is or isn't in place.

Here you can see the graph for the B jumpers and the three timing curves.

DETERMINING BEST JUMPER SETTINGS: The best setting for my bike with a standard stator coil is all jumpers removed (which is the way it will come to you). Test the settings for your bike to see what works best. Jetting, porting, compression, and exhaust pipe all affect the needed timing. Test jumper A at idle and going up hills and test the B jumpers for top speed on a level road. Which ever jumper setting allows the highest mph is the setting you should use. 

HOW TO UTILIZE THE JUMPERS: Just remove the boxes 4 srcews with a small Phillips screwdriver. If your screwdriver doesn't fit in the screw head properly then it will slip when turned. Don't go any farther if this happens. Go directly to a store and buy a fine-tipped screwdriver that will work properly. Otherwise you will ruin the screw heads. Once the box lid is removed you can see the black jumper locations. The jumpers (which are loose in the packaging) can be easily placed onto the receptors by hand or with a needle nosed plier. Keep the removed jumpers in something that is sealed such a a zip-lock sandwhich bag so you won't lose them. Once you settle on jumper settings you can remove the protective strip from the double backed tape on the box lid and adhere the box to your bike frame.