Assuming this is a single datastore:
Capacity = 720GB
Used = 304GB
Available = 415GB
Red Threshold= 108GB (estimate)
Org vDC Storage Policy = 750GB allocation, of which 746GB is used (4 GB free)
not this value is a fictional number. it's how many GB of VMDK is provisioned in VMs inside this Org & Profile/Policy. There is NO relation to actual free space here.
Thin/Fast provisioning is probably messing with your head a little (hence why used is so low and provisioned is so high).
Just know, when I create a VM:
Check 1: will the VM fit within the storage policy? e.g. the entire VM is smaller than 4 GB including swap etc
- I'm pretty sure this will fail based on your setup. If there was more free move on
Check 2: can the VM fit inside a single datastore's free space. Free = Available - Red Threshold
415 - 108 = 307GB
Is the VM smaller than 307 GB? yes, then this datastore is eligible for provisioning.
there are other checks, but these are related to space requirements.