Ideally, the mean of the mesh points should be close to 0.000 mm. I think things work out best homing the Z Axis at the center of the bed.
If you home in the center of the bed, you can look at the G29 T map to see which corners are too high (or low) and adjust them.
If you home in the center of the bed, you can look at the G29 T map to see which corners are too high (or low) and adjust them.