If this is possible, please replicate the Share Size (used) column (FrontView->Share->Share Listing)from SPARC on to the x86 based units? With the ability to display the Share Size Used as either: MB, GB or TB.
I do not see that column under Shares > Share Listing in Frontview. Are you using the EOL Share Security Mode? Please note that that security mode is incompatible with many modern OSes and not available on x86 ReadyNAS.
When Share security mode is used it is easy to tell the usage on a share by share basis. Not so, when using other security modes.