I've looked at it a few times but it's just not clicking with me.
Manual corrections required: 0.00 turn up (0.00mm) .38 turn up (-.19mm)
This is the dual z sync, or at least the start of it from what I understand.
So that means left is used as 0, but the right, do I move it up or down? It's currently .38 compared to 0 so I need to turn it "down" -.19?
it sounds to me that you are trying to use the auto leadscrew adjustment, but you haven't connected the two Z motors to different drivers. So it is giving you instructions for manual bed levelling instead. When it says "0.38 turn up", "up" refers to the bed. So it means you need to turn the screw to raise the bed or lower the gantry on that side. The figure "0.38" will only be accurate if in your M671 command you told it the lead of the leadscrew in the P parameter.