Students receive Student IDs before they receive Internet IDs. The Internet ID will not be created until the student's PeopleSoft record is flagged as matriculated. This usually happens very soon after the student's confirmation payment has been processed.
Matriculation definitions:
U of M: the time a student has submitted his or her deposit for attendance.
Merriam-Webster: "to enroll as a member of a body and especially of a college or university"