Unity 300 MAX LUN Size

Hi,

i have a EMC Unity 300.

I created a Pool of 12 disk of 4TB (RAID6 10+2), total size 41,7TB.

The problem is that i can't create a single LUN of 41,7 TB but only of 40,8 TB and and the Pool remain 429GB free.

How can i use the total pool size?

Thanks a lot