Put the table at one extreme of X, and Y in midrange.
Grab the end of the table and pull backwards and forwards, then you will see how accurate the gibs have been setup.
With a lot of care and a surface grinder they can be set for very small free play.
You know when it is getting better, when you can no longer feel movement.
After grinding the gibs, and using for a few days in production, and tightening gibs, mine is getting getting better. The ground gibs are bedding in nicely, until they wear again.
With the table at one end you get the total of X and Y slack and when you get it down to 0.003" it can start getting tight spots.
Before I had a surface grinder to do the gibs, it was hopeless.
Z gib is tapered, so much harder to setup and grind. One day....