A user in Easy Redmine is generally understood as an active user account, which means someone who can log in using a password. Accounts that are locked are not considered to be active users.
If you don't have the authentication set as required - Easy Redmine is open to anonymous visitors without login - they are not considered users.
Example: A team that uses Easy Redmine has 20 people. The system provides limited access to 50 clients who can submit tasks without having to log in. For this use, the license for 25 users is sufficient.
However, if the clients have user accounts, by which they log in, you would need a license for 100 users.