Wrong X coordinate with the local coordinate system? I would like a little bit of help with Blender 2.8. I don't know why the X coordinate of the highlighted vertex is -2 in the local coordinate system ? I think it should be something like -3.4 ?
Y and Z seems ok, but not the X.
In object mode, do Object/Apply/Scale. The local coordinates will now match the global coordinates.

Scaling an object in Object mode isn't a good habit, especially with non uniform scale (ie, not the same scale on each axis). You should avoid this, except if you have a good reason. Instead, you should scale your object in Edit mode.