The Gradebook Icons, which denotes which assignment types are used in the Gradebook Setup and are displayed when:
  • The teacher has chosen that assignment type in the Gradebook Set up
  • When the Gradebook has been setup up for the year.

Both items must be completed.

If it's set up by marking period, the teacher will not see the Gradebook next to the assignment types in the drop-down.

If you need to change how your Gradebook is set up reference How can I change my grade book setup?