How does the Mendix application differentiate betweeen internal and external users

Dear Mendixers,   I see in this post that internal and exernal users are determined by wether the user are within your company or users outside of the company. My question is: how the Mendix application differentiate this?   The reason why I ask is because I work in the Sandbox now with 1 internal and 9 external users. I know that you can have maximum of 10 internal users in the Sandbox or 100 external users. This means I should be able to create another 81 external accounts, but I can't create new accounts anymore. This means the system counts all accounts as internal and I need to change that to external to be able to add the remaining accounts.   Thanks for reading and your support!   Kind regards,   Paul
1 answers

As Rom mentioned in his answer for licensed applications this is true the 1:10 ratio. 

Sandbox is limited to 10 users, no differentation between internal and external users.