Well, I have to do a mesh in millimeters, and amplify the view to begin, and set a vertex in the center (Y=0 X=0), and as you can see, set the top view, and create a square of 10cm but the mesh does not fit the grid. See the first image please.
But when I fit the selected vertex to the grid, result in this:
On the job will be a mess if I leave that 10.1367cm, because y need exact precision, and I set Scene >>> Units >>> Meters and Unit Scale to 0.1 and 0.01 and 1... nothing!
The scale to 1, 0.1, 0.01... nothing!!! And what I need is a grid with exact measurement in millimeters.

