GEN 3 Space Discrepancies

I have a GEN3 connected to a Windows 2012 r2 server. The enclosure has 4 - 4TB Seagate NAS drives installed. I am getting a yellow warning light on drive bay 1 (one) telling me that I am running out of space and I should replace the drive. When I check the capacity of the enclosure, it shows that I have used 89% of the drive. Yet when I walk through the drive I have barely used half of the available space. I’ve walked through and removed unnecessary files, but nothing seems to help. What can I do to fix this issue and get the enclosure to report the proper capacity on the drive and to remove the yellow warning?

Please use drobo capacity calculator:

Available space depends on disks used and redundancy setting (1 or 2 drives).

OK, I used this before I bought my Drobo. It says that I should have 10.89 TB of available space, yet I’m only using less than half of that and getting out of space errors on one drive. The Drobo app is also reporting that I’m near my capacity, yet I shouldn’t be. So what do I do now?