As Sam mentioned follow what the VMware OS says for free space, not the EQL GUI.
One thing on UNMAP. If you are replicating volumes using EQL replication then UNMAP will not work.
Or if you upgraded your Datastore VMFS version from v3 to v5/v6. UNMAP isn't supported then either.
That only is applicable if you have been running VMware since 4.x days and just keep upgrading.