thats probably when Grant over revved it, but cos he has to put the clutch in, the power probably dropped loads, so at the end when he goes on the computer he edits what the graph displays and must have chosen not to show it past 4500rpm because it weren't relevant. i actually thought they had a rev limiter set at 5000-5500rpm
its mad when you watch the computer zooming in on the plot, it goes down into like single figures