[PS] C:>Get-MailboxDatabase -Status | ft name,databasesize,availablenewmailboxspace -auto
Name DatabaseSize AvailableNewMailboxSpace
—- ———— ————————
MB-HO-01 18.26 GB (19,604,766,720 bytes) 9.544 GB (10,247,766,016 bytes)
MB-HO-02 15.63 GB (16,785,670,144 bytes) 3.696 GB (3,968,761,856 bytes)
MB-HO-Archive-01 648.1 MB (679,542,784 bytes) 134.6 MB (141,164,544 bytes)
In the example above the database MB-HO-01 is 18.26Gb in size but has 9.544Gb white space due to archiving that has occurred. If you want to reclaim that disk space then the file can be shrunk by using eseutil to defrag it.