Visualizations are updated on a daily basis, and are based on counts of titles in the repository. Note that not all records in HathiTrust have call numbers. The call number visualizations represent about 60-65% of the entire corpus. The full corpus is represented in the date and language visualizations.
Currently Digitized statistics are also updated on a daily basis. The number of total volumes and volumes in the public domain reflect actual counts of volumes in the repository. The numbers for books and journals are counts of titles, not volumes (more than one volume is often associated with a given title). Other metrics are calculated based on an average book having 350 pages, being 3/4 of an inch wide, containing 47 MB of information, and weighing 26 ounces. The miles calculated are miles of books standing side-by-side, as they would on a shelf.