The opportunities screen does not filter out opportunities that have been filled.
"CiviVolunteer allows volunteers to sign themselves up for opportunities that you've defined. Each time someone signs up, CiviVolunteer creates an assignment. It also makes sure to offer only the opportunites which have not yet reached the desired number of assignments (so that you don't overbook anything)."
Also despite using project number all projects appear? Should it not be limited to project 6?