The team size is chosen when you create your Team. The default size is 5 teammates.
team size is the number of paid seats in your subscription
a teammate is a user with full editing rights that takes a paid seat
external users that were invited to a board with editing rights are automatically considered to be a team member
As an administrator, you can add or remove teammates at any point during your subscription period. To do that choose the Members section in the Team account settings. There you can see all the people that you invited and whether they accepted the invitation. A vacant seat is considered to be taken when you send out the invitation.
Team members menu
To add more people to the team click Invite new members and enter emails of your future teammates.
Invitations menu. Note that all invited will take a paid seat with editing rights.
Add members in bulk option allows pasting a list of emails at once.
Invite from domain option allows authorizing Gmail contacts to enable auto-suggest to quickly add email addresses.
All invitees will receive an email notification and will be able to join the work right away — the invite will be active for 30 days.
It is also possible to invite people by simply giving them a link. They will be able to create new boards and edit boards that were previously shared with the whole team. Teammates invited via the link will also appear on the list of Members.
Send out the link from the Invitations menu and your teammates will have instant access to your team's dashboard.
When the invitee clicks on the link you sent to them (or the one in the notification email), they will be suggested to sign up in RealtimeBoard (new users) or log in their RealtimeBoard account (existing users).
If you accidentally send an invite to the wrong email address or make a typo and now want to delete the extra invite, you can do it by switching to the Invites section and going for the three-dot menu > clicking Remove from Team:
Removing a pending invite from the team
If by adding new members you increase your Team's size, you will be charged immediately for the added seats. If you have vacant seats during your subscription period and add a new member - no charge is applied.
The cost of the new seats is prorated for the time remaining in your current subscription period (accurate up to a day), so your renewal dates for new seats will always coincide with your existing seats.
To remove users from your team account please see this article.