gen 3 wants to create 16TB volume but i only have 8TB...

hey yall
when formatting my 4-bay drobo gen 3 through drobo dashboard it gives me one option, HFS+, since i am running osx. this is fine with me, but it states that it will create a 16TB volume but I have only installed 4x2TB drives. Now, in finder, the volume size is reading 17.59TB available.
How can I format this through drobo so that i can do a proper RAID or similar setup that reads my drives accurately?

brett.

This is how drobo works.
http://www.drobo.com/how-it-works/

What you are seeing is normal.

What you are seeing is perfectly normal. This is because all DROBOs use a technology called Thin Provisioning, so it does not matter how big the logical volume is. Drobo will allow users to increase their capacity up to 16TB, especially with the 5 TB and 6 TB drives becoming more available this year. This is how DROBO is able to expand and increase the space on your volumes.