This probably won't help, but here's what I know.
For one of my rigs running LinuxCoin, which has three 5970s (6 GPUs total), the OpenCL devices (GPUs) are identified as follows:
[cl:0:0]
[cl:0:1]
[cl:0:2]
[cl:0:3]
[cl:0:4]
[cl:0:5]
I do not know what the first number after "cl" means or how it could be anything other than 0. See, I told you this might not help.
I always thought the first digit after the "cl" refered to the platform of GPU you have. Like you'd see different numbers in there if your rig had 5XXX series cards mixed in with 6XXX series cards. iono for sure though.