Disk-based Storage Total capacity

I am using Backup Exec 2012 with a Data Domain system that has in total (3.6 TB)

I am using the Data Domain for creating 2 CIFS shares.

From Backup Exec I create 2 "Advanced File Type Devices" pointing to each of those shares.

Each time I create and "Advanced File Type Device", the reported size is 3.6 TB (the total size available).

The Disk-based Storage reported by Backup Exec is 7.22 TB which is clearly incorrect as the total size of the Data Domain is 3.6 TB

Is not Backup Exec aware that both of those "Advanced File Type Devices" are pointing to the same device and the space is shared?

Can someone clarify how it works?

Thanks in advance.