You can confirm a session as soon as you create it or when you have enough people enrolled in this session.
The confirmation process varies based on the policies and procedures of your company. The following are the ways the confirmation works:
If you confirm as soon as you create a session, when an end user enrolls they only get one email with an Outlook calendar invite confirming their registration.
If you confirm as soon as you create a session, and you do not get the minimum required, the course may be canceled and a notification sent.
If you do not confirm the session until later, the end user will get one email indicating that they enrolled, and a second email with an Outlook calendar invite saying the session is confirmed after the session actually gets confirmed.