When a customer deployed a vApp into Cloud Director they got a warning about their storage quota. At first we couldn’t figure out why this happened because the vApp should easily fit.

But once again, RTFM! In the documentation there is a section about this:

When you deploy a vApp template, VMware Cloud Director reserves in the VDC the full provisioned size of the template even when the actual disk size is lower. You can switch between this behavior and VMware Cloud Director using the actual disk size instead for operations, such as importing vApps and vApp templates, importing templates from vCenter, copying vApp templates, and moving vApp templates. To change the VMware Cloud Director behaviour, you use the VMware Cloud Director API and run the following configuration PUT API /1.0.0/site/configurations/urn:vcloud:configuration:storage.template.quota.useActualDiskSize with the following body.

{
  "name": "storage.template.quota.useActualDiskSize",
  "typedValue": {
    "value": "true",
    "type": "StringEntry"
  }
}