I was very suprised to see such a serious error in GstarCAD. When I summarize several areas with a tool MEASUREGEOM, it was not the same as the calculation of the whole area. I was checking for a bad click of mine but I discovered an error in the software. Later on, I found out that even if you click inside the same shape but at different locations, you can get different area! Thats insane for such a professional software. Developeres recognized the problem but I realy do not know when it will be resolved. Meanwhile we pay for the software but we cannot reliably use one of essental functionality. And right now I need that tool quite urgently.