Unit
The default primary measurement unit is items. You can change the measurement unit (See Measuring in image files/Types & method of measurement/Object count/Factor).
The unit defined at this field is the one of the
primary measurement and it is only used when the measurement is not linked with
any WBS work items. If such is the case, then the default unit is depending on
the type of measurement and changing it is only meaningful when using a factor
to, for example, convert the number of objects to weight (Kg) or area (m2). If
the measurement is linked to a WBS work item then the measurement unit is the
unit of the linked work item.