figuring out advance timing

edit. I think you're on the right path.
See if Holley has left side of the table as Vacuum, or absolute pressure.
I could see them doing vacuum, but my understanding is that pressure is usually shown directly from the MAP sensor.
In which case atmospheric pressure is around 101 kPascals at sea level.
If so, then maybe that's the issue, not low vacuum.
Assuming your table is showing MAP, then vacuum would be roughly the brown numbers