That is pretty close but if you want to get it closer the z axis is (should be) easy to fix. For the most part it is only the 4 bolts. After that it gets really complicated. The stainless one I just finished has so much less give, it took me two tries to get it square within a 1/16″ over 2′ at 1/16th” I can shimmy it before I start an important cut. After I put a few hours on it I will take the belts off and try and get it to at least half that.
So, put some time on it to break things in or let the plastic stretch or whatever happens. Take the belts off, and readjust the center. I check all the middle bearings for tension by rotating them with my thumb. That really shows you what is tight or loose. On mine it really came down to just nudging some of the nuts.
Remember that is amplified over the length of your z travel so if it was half as long it would be less than half as far off. Tangent or something math related like that. How far off is it at what length?