Windows DPI is 125 % (you need to sign out from win 10 then sign in again in order to apply the setting successfully).

Diagram is hosted in RibbonWindow.

The diagram ruler does not show the ticks and labels on the left of the zero tick (label). The Position property of Diagram could (0,0) or (500, 0), (300, 0) etc...

Check the attached image for better illustration.

Workaround could be replacing the RibbonWindow with MS Window.