There are 5 predefined roles you can chose from. However there is also the company admin. See: https://docs.mendix.com/developerportal/companyadmin/
I think this is ment to be the 6xth role.
Mendix team already corrected this. The correct answer is now 5. =)
You can also find more details below :
https://gettingstarted.mendixcloud.com/link/module/79/lecture/510/2.4-Project-Roles