Timing Tab Question?

[RxPx33]

Here is my timing tab. I just installed a new HEI and borrowed an inductive timing light from a friend. How do I read this tab? I see where the 0 mark is but what does the A and the R stand for?

From what I read on here I want to get 8-12 degrees on idle.

Is that towards the R or towards the A?

Im new to all this so thanks in advance for any suggestions or help.

[lts70]

A- Advance

R- Retard

[long67]

Go towards the A. I think that might be 2 degree increments.

[RxPx33]

So I go 8-12 degrees to the left or counter clockwise on the balancer?

Also is each mark 1 degree or 2 degrees?

[RxPx33]

Thanks guys this helps out a ton

[bk2life]

When someone says
their initial timing is set at 10 degrees,
that means the distributor is set to fire
the spark plugs when the crankshaft is
10 degrees of rotation before the piston
reaches top dead center, which is 10
degrees of advance. This is the “initial”
or “base” spark timing which is checked
and set at idle during a traditional tune-up
(with the vacuum advance disconnected);
it’s fixed at the point where it’s set by
clamping down the distributor holddown
bolt, and doesn’t change – it’s
always there.

[RxPx33]

I loosened the Distributor this morning and used a timing light to set it about 10-12 degrees of advanced timing (with the vacuum disconnected). It was rough trying to get exactly 10 or 12, because those marks are so small. So I figured as long as it was between those two marks it was good. It idles much better now than it did before I timed it. Once I got it tightened back down I rechecked the timing to make sure it didn't change. I reconnected the vacuum and then set the mixer screws on the carb to make the idle sound better and adjusted the throttle screw.

Thank you to everyone on this site for your advise and help. I know very little about engines and old trucks, but with this site I am able to do a lot of things on my own that I would of had to have someone else do for me before. So thanks again.