As Hank said, the dial-back timing lights are great, that's what I use... alternatively if you don't want to shell out the $60-80-100 for one, get a timing tape of the appropriate length to afix to your balancer... these go for less than $5 and you have marks all the way around...

As for the other question, the retard knob (that term always makes me giggle, I know... immature but what the hey ) retards/advances timing all around from initial to total... just take what you have and subtract/add to it everywhere.... the device actually only retards (can't predict the future) so at the maximum setting (15) is where the ignition system would be without the box.

Hope this helps...

Chris