A number of club have away tickets with more than one bar code stub which is detachable. If its an adult ticket both stubs are in place, if its a concession the first stub is torn off to leave the second bar code. Therefore the turnstile will know the difference.
I caught a glimpse watching the game on TV yesterday, looks like a good ten seats either side covered in netting - although that was against them up the road with their drum and droning.
Just found this, you can just see the left hand side of the netting