in the first box, put the mac address without the colons. Ignore the second box, and in the third box put 0800
I think that should do it for you.
I do have to say that the documentation on this is a bunch of crap. The router looks very confusing a little outdated too, but that is just my opinion.
You do have another option with building a PC router/DHCP server and blocking it within that configuration.
good luck to you and let us know if it doesn't work.