Sources in Clooz refer to a description of the document (book, certificate, journal, etc) the information came from. The Source Title is the exact title of the item, such as from a book’s title page or cover). The Source Label is any form of description you choose to use to identify the source when it appears in lists of sources in Clooz. This is usually some form of composite of location and document type, such as Pennsylvania, Lebanon County, 1850 U.S. Census or U.S. Census, 1850, Pennsylvania, Lebanon. The trick is to determine a system of labeling you want to follow that results in your desired grouping and ordering of the sources when display in an alphabetical list. Labels are not used as part of citations, only in lists of sources.
Note that you can select whether Titles or Labels are used for sources when appearing in lists within Clooz by going to the Edit menu->Options item.