Starting from vSAN 8.0, a new data field was added to the output of the "esxcli vsan debug object list" command.
This new field is "Used 4K Blocks:" and it's the most accurate value when trying to identify how much a vSAN object is consuming, for example:
Object UUID: 7536ae61-fe2b-e371-78e0-020096059a9c Version: 15 Health: healthy Owner: sc2-10-185-244-1.eng.vmware.com Size: 1024.00 GB Used: 5.59 GB <----------------------------- old counter Used 4K Blocks: 1.35 GB <------------------- new counter, already showing a huge difference
The Cluster level vSAN usage information, found by following this path in vCenter "Cluster -> Monitor -> vSAN -> Capacity", has been confirmed to be showing the correct value.