Assuming this is first unit in the VC (member 0), the 0/0/0-0/0/23 are the 24 1/10 SFP/SFP+ interfaces. The 4 x 40GE would be 0/0/24-0/0/27. When you channelize these ports are named 0/0/26:0 - 0/0/26:3. See:
I would suggest you use 1st 2 QSFP+ (24 & 25) for VC connections, as by default this come enabled as VCP interfaces.
Run show virtual-chassis status to see this.
The first expansion slot is PIC 1, 0/1/0-0/1/7, and 2nd expansion is PIC 2, 0/2/0-0/2/7.
OK?