Capacity Different in Dashboard/Finder

My Drobo Dashboard app is showing I currently have 3.54TB of available space on my B800fs, but when I am browsing the device via Finder it shows that I only have 1.66TB available. Which of these numbers is the correct one?

I have dual disk redundancy enabled.

Use the Drobo Dashboard, it would reflect the most accurate reading on your usage/available space.

Thank you KelvinY

Actually, now that I have gotten within 500GB of what Finder says my Drobo capacity is, Finder will not let me copy over that limit, even though Drobo Dashboard says I have 2.54 TB of 18 TB available.

Is there a way to make Finder let me copy more than what it thinks my limit is on my Drobo?