I have setup a server with LVM, and at first I juset created a small logical volume named 'root' of about 10GB, but later changed my mind. I extended it to 1TiB, but my server still is in two minds of how big the partition (or mountpoint, I'm not sure) actually is.I used the #lvextend command in the console to extend the logical volume, not through webmin.Here's a screengrab from webmin that maybe shows it more clearly.
Extended logical volume in LVM still shows old size
lvm
I'm guessing you're expecting more free space... lvextend resizes the logical volume, you also need to resize the filesystem:resize2fs /dev/Hulkvg/root(as root; I don't know how to do that through the Webmin interface).