VMware vCenter Server 8.0
VMware vCenter Server 7.0
Smaller deployment size cannot be selected if the amount of resources currently in use exceeds it's default value.
In this case, the storage allocated size of the source VCSA VM (628GB) is over the default value for Tiny deployment size (579 GB).
The current allocated size can be seen in the Summary view of the VCSA VM via vSphere Client.
If a snapshot has been taken and it has grown too large, delete it and rerun Installer.