I created a Cohort with one user. I enrolled that Cohort into a course through Cohort Sync Enrolment method. Later on, I went to bulk manual enrolment form through Manual Enrolments link. I found that user (part of the same Cohort) in the list of "Not enrolled users", on the right side. I enrolled that user from Manual Enrolments too.
After doing this, I saw user table on the Enrolled users page. There were two different enrolments (different time and method) for that user in the same course.