Help with 28oz external balancer and timing

Have a spare 28oz external balancer for later SBF 302 - looks like the attached.

Couple of questions I'm hoping folks can help me with:

1. Does anyone know how I should be reading the timing marks on this one? Why are there two scales? What does each represent?
2. For roughing in timing, would it be something like 10-12 degrees BTDC at idle with about 34 degrees BTDC at full advance (~3,500 rpm)?



Cliff there are several options & types of timing pointer and locations of TDC, to be really sure you have the correct combination you need to ascertain that #1 piston is at TDC and whichever timing cover or bolt on timing plate you have lines up with #0 degrees at that time.

Some of those combinations are made for Left or Right locations of the bottom radiator hose in order that you can see it with light & engine running. Once your satisfied with that you can start with your ~10 deg initial and ensure you have around 34deg max at say 3000rpm.( all without the vac adv hooked up.)