You can deletea user from Confluence if they haven't yet added or edited any content on the site. Content includes pages and blog posts, and edits and comments on existing pages.
If a user has contributed content, you should disable their user account. Disabling a user account won't remove the content they've created.
You can edit the groups that a user belongs to, to change their permissions without completely preventing their access to Confluence.
Multiple user directories –
Number of users and your license – The Confluence 'License Details' screen tells you how many users your Confluence instance is licensed to support, and how many are currently registered. The number of registered users includes only users who have the 'Can Use' global permission. Deactivated users, as described above, aren't included. Choose Refresh to make sure you see the latest count.
If the user resides in a Read Only external directory, the option to disable the user won't appear.