I think I have the issue. So, when setting up the virtual disk, you have to set a maximum size (despite it allocates directly all that space or it is dynamically allocated). So, at first I set that at 10GB, then i changed that to 25GB. But of course, the system still knows that its partitions are of 10GB, so probably what i really have is some unformatted empty space there.

Not sure if i will try to install gparted an try to resize the partitions, have to check if you can really do that without wipping them, or most probably I will restart the process completely and create a new VM with more space.