Wrong display of millimeters?

[Lagos11]

Hello everyone, as a new user I have a simple question that is currently bothering me. I have not found an answer yet.

I have an existing floorplan with existing dimensions from an original plan.

The exterior walls of a house are 37.5 cm thick.

One side of the house is 12.885 meters according to the original plan, i.e. 12885 mm.

I have selected the unit of measurement millimeters in the settings.

In the "Modify walls" settings this is all displayed correctly (see screenshot).

If I now automatically calculate/add the dimensions of the walls by double-clicking, it is always rounded up to 12.890 or 380, which is unclear to me with the millimeter accuracy set.

This is very unpleasant, because that deviates then from the original plan, even if only minimally.

Why is it displayed correctly in the Modify walls settings, but not in the actual plan?

Is this a bug, or do I have a comprehension problem here?

Thanks!

[Daniels118]

Maybe the right side of the dimension line snapped to the side of the other wall, not to the end of the one you are measuring.
Try to delete the other wall and draw the dimension line again.

As a general rule two walls ending in a corner shouldn't just overlap, but must be merged;there is an option in the plan menu to merge the selected walls.