You can also go into the user's mailbox in Outlook and see the current consumed space by right-clicking the top-level object - usually the users email address or name (just above the Inbox typically) and selecting "Data File Properties". From here click the "Folder Size" button. This will show you the Total size as well as a breakdown of each folder and its sizes. This will help identify where the consumed space is located.
Get-MailboxStatistics "<Enter Alias or DisplayName>" | FL TotalItemSize