Vreejan,
To augment Brett's response to your excellent question...
Delphix Express has no control over how much storage is
allocated to the guest virtual machine by the host hypervisor, but Delphix Express can indeed control how much storage it
manages once it is installed and configured within the guest VM.
So, as Brett explained, the 25 GB limit is for dSources, VDBs, vFiles, and all other data objects
used and managed by Delphix Express.
Hope this makes sense!
-Tim