Vertex Nano, prints too large and too small

Hello all,I am starting out finding my way around the tiny Vertex Nano printer (belt x and y, threaded rod z, no heat bed). Prints are actually coming out decent. This is nice.

So, as far as my metrology allows, it seems my x and y dimensions are ~0.2 mm too small while z is ~0.6 mm too large. I have not done a lot of prints, but this is true for different sizes so I'd say these are absolute, not relative, errors.

I use the Addnorth PLA filament, untouched firmware / printer settings, and no spectacularly odd slicer (cura) settings. For the X and Y, I possibly underextrude, will have to check. The large Z may be related to printer hardware, there is a slack in z axis motor mounting but I feel 0.6 mm is more than expected if this is the explanation. I am trying to remedy this though. It's a little bit hard to reach (and the shims I print have weird heights, as it were.)

Any suggestions to things to consider or try? Thanks!

adjusting the stepper motor steps in the firmware will probably sort the problem.

Thank you. I think this is not the problem. If I am correct that the error is fixed rather than a percentage, steps setting isn't the issue.