Need help on sizing differences of FreeNAS - ZVOL Volume

[dsheridan_wc]

FreeNAS Volume listed under storage does not show correctly.
Storage | Volumes | pool00 | RR-Repo-ldi01

The ZVOL is set to 9T but showing Used 18.2 Tib (45%) and Available 21.4 Tib

See screenshots. Could someone help me understand why the differences?

 

[dlavigne]

Did you find the answer to your question?

 

[dsheridan_wc]

I have not. I have this question posted in Experts Exchange as well and no one has answered.