The number of smrtDialer seats you subscribe to reflects the number of users who can dial campaigns at the same time.
We purposefully have left those seats unnamed, so any User with the applicable Finance and Billing Permissions can swap Users in and out of the seats. The seats are not tied to any specific user.
All Users will have access to see smrtDialer, but only those assigned to seats and Campaigns can actually make calls using the power dialer system.