Hi Kira,
I think your're confusing things
Check Used Space, and not the provisioned.
Also check the size of your Replica Image.
Instant-Clones are storage efficient technology, so you can have hundreds of VMs in 5TB datastore.
You can check the sizing guidelines here: Sizing Formulas for Instant-Clone and Linked-Clone Pools
Just follow the guide, and as is Instant Clones, don't use Persistent Disks.
Another good point is to use Thin provisioning in your Master Image.
As part of the optimization process ( Creating an Optimized Windows Image for a VMware Horizon Virtual Desktop | VMware ), you have to use sdelete tool, it overwrites all empty disk space with zeroes so that it's possible to shrink the VMDK later.
Doing that you have a smaller Master image and hence a smaller replica, and so on.
I have a Windows 10 VM configured with 60GB disk, and after all the optimization process, I have a Master Image using only 24GB.