You have removed several backup archives or have backed up a significant amount of data to the Cloud, but the Storage Usage still displays old values.
Statistics are recalculated every 8 hours; then the new values are displayed in the Management Console and Backup Management Console (both for Acronis Cloud and Service Provider hosted storage based on Acronis Storage or Acronis Storage Gateway).
Note that backup size/usage values in Devices view and in Backups tab are calculated by different Acronis Management Server services, so these values can sometimes be displayed as different. These statistics are also refreshed every 8 hours.
Other possible cause is that some old or incomplete backups occupy storage.
Check the Cloud storage for any incomplete backups: see this article for detailed instructions. Incomplete backups are stored to enable Resumable Backup, a technology that allows using the already uploaded data to continue an interrupted backup operation. This technology works for disk-level backups only. In future releases, Acronis development team is planning to improve this behaviour by enabling all types of archives to be resumable. To further improve the usability, we are planning to implement management of incomplete backups from the Backup Management Console directly.
If customer have removed the machine (unregistered it) but haven't deleted the account, the data remains in the Cloud storage, but is not shown under other non-administrative accounts. If you no longer need this data, remove the unused accounts (archives in the Cloud storage will be removed upon account deletion) or log in to Web Recovery Console to clear the surplus data.
Wait for up to 8 hours for statistics recalculation. If the numbers do not match after a significant period of time, please contact Acronis Customer Central with a reference to this KB article and screenshots indicating the issue. Real-time storage usage statistics will be implemented in future releases.