In general terms extension is controlling the actual main function of the damper, that is to say the initial control of the spring oscillation. If it's too soft the car will bounce too much, if it's too stiff the car will react to bumps too slowly and the car will 'hop'. In terms of weight transfer running a stiffer front extension means that that the weight is slower to move off of the front wheels both under braking and acceleration. If the damper is compressed and the extension stroke is stiffer it takes longer to return to centre since it is fighting against a greater resistance. Although if he's having a real spinning problem dampers aren't his problem. Dampers are only really for fine tuning weight transfer, the other parameters are far more effective for altering the handling characteristics of the car.