It advances the timing and raises the RPM. I always just leave mine out. The timing advance is overriden at 2200 RPM IIRC
Ya know, I just figured something out. In all their charts, Bosch never uses exact figures because the high idle/etc can all be set to different things. For instance, on a stock pump designed to rev to 5k rpm, it looks like the advance of ~2.5 degrees would start increasing again w/ the CS out after 2200rpm like ya said, but if the pump only revs to 4k rpm, or up to 6k rpm, because of the lower or higher high idle, then the KSB timing cuts out at a proportionally lower or higher engine speed.