His miner is probably displaying the wrong numbers, no idea why tho. I'm willing to bet whatever pool he mines on reports closer to 600kh/s per card. With major overoclocking djm said he was able to get 660-670kh/s
My miners must be submitting shares like crazy because the pool I mine at is reporting 5,000-9700 kh/s all day per 6 card 750ti rig