Hi Kristen,
As the admin you can change the 'Default New User Type' to email-only to prevent this from happening. By making this change you will have to manually change the type from email to full in the invite window whenever you actually want to invite a new user as a Full user. To quickly access this setting be logged into Clarizen and click the following link:
https://app.clarizen.com/Clarizen/Settings/DefaultNewUserLicenseType.aspx?CSRT=1862588507903486783