dataset inheritance and quotas

[disordr]

I'm using FreeNAS for serving user home directories and projects across our machines.
I've set up 2 large volumes, one for home dirs and one for shares.
Under the Shares volume, I've created a main "projects" dataset with a 25GB quota set (for that dataset and children).

I thought that even though the parent dataset has a limit of 25GB, I could create sub-datasets with larger quotas up to the full volume size.
This doesn't seem to work though.

Is it possible for a child dataset to have a quota larger than it's parent (as a one off), but others should inherit the parent quota?

Thanks,

Philip