Airport Extreme 5GHz option

I've just bought a new Airport Extreme, which allows for a guest network and a dual band 2.4GHz/5GHz network.

I noticed that the 5GHz network was not enabled by default. When I enable it, it seems the name must be different, and the default is the same as the non-guest network with "5GHz" appended.

This would tend to suggest 3 separate networks, but in the DHCP range config, I see only two options: guest and non-guest.

I also tried setting the 5GHz network to have the same name as the 2.4GHz non-guest network, but this was not accepted.

Can anyone clear up my confusion?