When you insert a scaled external reference with boundary objects into a drawing, any associative spaces generated from the objects in the external reference will not be correctly calculated when using an area calculation standard.
Currently, when an external reference is scaled during insertion, the boundary offset calculation will never be correct if the boundary offsets are calculated by an area calculation standard. You can either re-insert the external reference without scaling, or you can change the boundary offsets from By Standard to By Style or Manual and try to emulate the rules of the area calculation standard in the style of by manually offsetting the boundaries.