Veeam backup used size larger than storage size on ReFS

[cmklo]

I have a storage around 72TB size. Format as ReFS.
But when I check the folder size used by VeeamBackup, the size is 102TB. Large than my storage size, how is it happen?
My storage just a simple volume, not thing special on it.
P.S. Now my storage just used 20TB of 72TB, with more than 30 restore points and a few synthetic full backups.

[Gostev]

https://www.veeam.com/blog/advanced-ref ... suite.html