If you have a mounted share name of as0s2-20Gb the share will not display in the System/Home page Disk Usage Graphs.
It appears the - minus is affecting the graphical disk space usage graphs on the home page.
The mount works OK, just the graph does not show it.
Changing the mounted share name to ad0s2 does not make the mount appear until freeNAS is rebooted.
This 'rename/reboot' corrective action may also be related to bug No. 1631984 - Mount rename gives Guest and SCP Issues