Comment 19 for bug 1643383

@swulf - it looks like there may be a confusion here as to whether one is using a geometric bounding box (which does not include stroke width) or a visual bounding box (which includes stroke width). The dxf output will correspond to the geometric bounding box, which will be slightly smaller.
    If you draw a rectangle and inspect its dimensions immediately at the top you will see the 'geometric' size. When you switch to the Select Tool, F1, you will see its 'visual' size displayed.
    Alternatively, if you want to confirm the geometric size, open the menu item Edit->XML Editor. The width and height properties shown here will give you the geometric size which is what the dxf will use as well.