- Available from: Lets you enter regular start and end dates
- Available after: Lets you enter a start date; the test is then available until the end date of the course
- Available until: Lets you enter an end date; the test is then available starting at either A) the course's start date or B) the time you set up the availability, until the date you entered
- Always available: The test is available the entire time the course is in session (according to its start and end dates)
So, pick the option that best fits what you're trying to do...