Drobo Dashboard reports different USED capacity than Finder...

Hi, setting up a Drobo for backup.

I know there are a lot of issues with Lion and Time Machine and I/O connections with Drobo. Not my question. Nor does my question really pertain to the way OSX sees the virtualized expandable Drobo volume.

I've noticed that the Drobo Dashboard reports a different amount of USED space than Finder or Disk Utility does.

Finder will report what looks to be the correct amount. It's a clone of a drive, so it's essentially the same amount but with a small difference for over head. But the Drobo Dashboard is reporting much less space used.

The Drobo is set up to have 5.4TB of usable space. The disk I'm copying has 5.3TB. Finder and disk utility report Source drive and Drobo both to have (approx) 5.3TB used, however DroboDashboard reports only 4.8TB used.

Does it have to do with the overhead? Or is drobo compressing/archiving in a way that saves space? if this were the case, why wouldn't finder report the same amount?

Doesn't that make it less useful if Drobo Dashboard does not report how much free space you actually have?

If I look at the Drobo Dashboard and say "hey, I've got 500Gb free, let me dump 300GB more on here," but in reality there's only 100GB of free space isn't that going to wreak havoc?

So which is accurately reporting the amount a used space? Drobo Dashboard or Finder/OSX?

It's making me a little nervous because i've read about some issues with certain OSX apps getting confused by the virtual volume and trying to load up the Drobo when there is no more free space and killing the Drobo volume.

Thanks in advance