Having ramped up my intelligence to stupid levels in the process of just to see what zoology score I could get (that 600 one), there's a display error once it hits triple digit numbers.
Without looking at the code, I'd be surprised if it's stored on more than 2 bites, so it'd cap at 255.
I could, of course, be wrong. But I have no idea why they'd assign a higher number of bite places to something 20 is considered very high in.