Hello Johnny,

Only internal users do count when using enterprise 18 plan.

i prefer you would also check this forum where this query has been asked earlier

https://www.odoo.com/forum/help-1/odoo-enetrprise-user-licence-calculate-only-internal-users-or-portal-public-users-also-170072

If you're sufficied with the answer i have given upvote the answer.

If any query regarding this further you can ask here only in the thread.

Thanks