Total Zone enables you to graphically (or manual) indicate the length and width. In case of a rectangular shape, only the width needs to be set. The length will be automatically calculated.
The dimensions will be shown in your own units and can also be completed with the height of the room.
The dimension hotspots are attached to the zone stamp origin (where you set your zone stamp with the 'hammer' during zone-placement). So if you move the entire zone the dimensions-hotspot go along with it. The view-dependent offset is also related to the origin of the Zone Stamp.