If it's like the HD 7970, it can do I=18, even I=20....But on average, most single GPU cards can do at least I=18...I do I=80 on my 2x HD 5870's and HD 5850...
I=80!?
He's a failed troll.
You can't go beyond 20, as stated in cgminer.
You can, just need to do some modification..