You may wish to take a measurement in Workshop or download the OBJ file for a Space.
Measurements in Matterport are generally accurate to within 1% of reality under normal operating conditions. Decalibration, abnormal temperatures, and other factors may result in reduced accuracy.
For example, in a 10 ft (3 m) long room, measurements can vary within 1.2 in (3 cm) from actual.
In addition, objects smaller than 1 in (2.5 cm) in any dimension may not appear. This also applies to very shiny or very dark objects since not enough light is reflected back to form a 3D mesh.