who has this!???

[UnderdogGN]

im looking for some help with the MSD in-car adjustable timing control box. I was just wondering the basics on it because i bought my car and it already had it installed. It has a knob you can turn from numbers 1-15. I was wondering is that the total degrees of timing you are running? or would that be number of degrees added to your timing? Also, what is the procedure for adjusting it? Is it just an on-the-fly twist of the knob to change timing? thanks