Modelling precision in question. Strange dimensions

I am modelling far from origin. After i increased display precision when i got suspicious about correct dimensions i dont understand how exactly input lengths are not precise. Some of the numbers are exact and some of them are off by microns.
I really dont get it how i could obtain such numbers when i always moved/modelled geometry with exact numbers.

For example this is exactly 200mm

And here i have strange dimension. I am pretty pretty sure i offseted that big block from that plate exactly 50mm in Z.

My whole model is messed up. I understand there is tolerance (0,01 mm) but even though why some numbers are exact and some are total mess. Maybe x and y is tolerable since its transformed to world axes but how Z can be not whole number when its principal axis.

How far from the world origin?

What is the absolute tolerance setting? Have you changed the absolute tolerance setting since starting the model.

It appears that the CPlane coordinates are different from the world coordinates. Is that correct.

sorry i didnot respond. i think this is all related to far from origin problem. I added my post about this issue here: Bug? Rhino isn't accurate far from origin - #9 by ivan.galik