The cloud height shown in the graphical data (in feet) is not measured but is a theoretical estimation of the lowest cloud level, based on the conditions on the ground. Note that this is given, even in a cloudless sky.

the altitude of the cloud base above the local terrain or the difference in height between the cloud top and the cloud base; (sometimes called "thickness or "depth" of the cloud)

The cloud height (or the height of the cloud) is the distance between the cloud base and the cloud top. It is traditionally expressed either in metres or as a pressure difference in hectopascal (hPa, equivalent to millibar). Sometimes, the expression cloud height is used instead of cloud base, in which case the context has to clarify whether the intent is to designate the elevation or the size of the cloud.