3 marks on harmonic balancer...what??

Hey guys...quick question:

I'm working on an '83 slant that we did an HEI conversion on. The cap is oriented differently between the LB and non-LB distributors(I think) so I had to start over at TDC and drop in the dist there.

However....there are 3 marks on that balancer each 1/3 of the way around the balancer. The only difference is one mark is longer than the other two and both valves appear to be closed at that point. I say appear because this is a hydraulic engine and there's no slack in the rockers.

Is THIS the TDC mark?

That has to be something to do with the Lean Burn...


Thanks,
Tyler