VMware Reporting Disk Usage Beyond Allocated Disk Size

I have an NFS datastore where some VMs are stored, and one in particular is showing something odd. This VM has a 1.3 TB disk, but the flat VMDK file on the NFS datastore shows it is 2.1 TB in size. Any ideas why this would be? There are no snapshots involved here - this is the single -flat.vmdk file that is way larger than the specified size in VMware for this disk. Any way to correct it without creating a new disk and migrating all the data?