Used space is much bigger than real used space

Hi All,

I have a VM, which is used about 400GB but in the datastore, it shows the VM used 1.98 TB of datastore. Now I want to run consolidation for this VM but there is not enough space to run. I have tried to delete all snapshots but there is no luck because, there's nothing in Snapshot Manager, just only "You are here". Via console of ESXi, it is shown as below:

How can I solve this issue?