If I am not mistaken this probaly refers to the tolerances (the lower and higher acceptable dimensions of the diameter of the circle).
i.e. : minimum is 3.40mm, and maximum should be 3.53mm
In your particular example you need 4 thru holes within the tolerances stated above [3.40, 3.53].
Your question is much broad in my opinion, I'll stick with the most important aspects IMO.
Computer 2D drawing has limitations (no detection of crossing of invisible lines, dimension lines touching the solid lines, and lots of others), and cad programs simply don't care about these kind of things (and I hate this aspect, but we work with what we got).
Two thing to look at.
The first is your coordinate system. World coordinate system uses elevation 0 by default. Any line started not connected to anything will be drawing to elevation zero.
The second issue is if you have pre-existing line work like say a survey whose contours wer placed into the drawing with their respective Z elevations maintained. Same ...