Welcome to the SeeMeCNC Community

I went back through the calibration process on my rostock max v2 this morning and got better results that before.

I printed a 20mmx20mmx10mm cube when it was finished printing it measured :
20.03mm in x direction
20.19mm in the y direction
10.04mm in the z direction

Is this within the tolerance of the printer or should I be expecting closer results than this?

Are there other things I need to be looking at? Can extrusion fine tuning effect this?

Very good numbers except for Y.
We have had discussions about changing only one axis, perhaps one the heavy hitters on this forum
could give their opinions on tuning of one axis.

Make sure that belts are snug and that all points of rotation are lubricated.