It means you need Standard subscription if you want to have 6 or more, but less than 33 members in your network. Up to 5 you don't need a subscription, it's still free. If you want 33 or more members you need Premium or Multi-network.
With a Hamachi network computers are added to a network and would then be able to communicate with each other. A computer's online/offline status will not effect weather it is added to a network still. In other words, if you need 10 computers on a single Hamachi network, you would need a Hamachi Standard subscription assigned to that network, regardless of if they are showing as online or offline.
Like pz said, Hamachi free accommodates up to 5 computers on a single network, adding a Hamachi Standard subscription to a network would allow you anywhere from 0-32 computers on that same network.
I hope this helps.
Erik Elsom-Van Vogt Customer Support Representative LogMeIn, Inc.