someone please help me understand this.

I'm confused, Bill. "numbers to the left" means nothing I cannot see what you are seeing. You have GOT to determine whether they are up or down. Don't get confused by "level" the point is you want one shaft in relation to the other, PERIOD.

But to compare them, you certainly need to reference them.

To put this yet another way, the car does not need to be level. You could for example jack the car so that the CRANK (pan rail) is level. That then would be zero, and you can simply then compare the pinion to that zero.

The point is it does not matter as long as you can reference the crank / transmission centerline (pan rail) to some point, and then compare the pinion. But you certainly need to determine up vs down.

I tend to "simplify" things in my own pea brain. I have one digital level which "is not clear" in my mind which way. So I usually tip it until it zeros, and then tip in in a direction which I "know" is up or down, and notice which way the reading is going.

Or hang the gauge right next to the pinion, EG, and level it and look at it which way the pinion is tipped, etc in relation to the gauge.