This is an issue for your IT staff. If you have a multi-user license, then sharing the activation for the Duxbury software is an efficient way of making use of your resources. Some users may want exclusive use of a single activation, other users may want to pool their activations. On this screen you determine the number of activations that will be shared from this host computer and the port number that the activation service will use.
The most important advice is that if you do not know the meaning of one of the prompts on this screen, you should consult one of your local network administrators.