This is a template attribute. Template attributes can be used in filtering, or to retrieve data from the model to use in drawings and reports. For example, when you create a report, Tekla Structures replaces the attributes added in the report template with the corresponding object property values.
In drawing templates, this template attribute shows the revision mark
entered in the Mark box of the last revision of the drawing in the Revision handling dialog. In REVISION
lists, it also shows the entire revision history.