Error with Backup LUN on NetApp with NDMP

Hi Experts,

I configured Symantec BE 2012 connected to Netapp 2240 via NDMP protocol . This Netapp is used to store VM image. 

When i create the Backup job for LUN on NetApp , BE 2012 read all the LUN, but the LUN size is so smaller than actual size on NetApp.

Read the attached file.

Could you please explain me why it is smaller than the actual size of LUN on NetApp and how can i fix it.

Thank you.