In order to get the green checkmark, learners are required to attempt all assignments, including ungraded and optional assignments with submit buttons, read all content, and watch all videos to 90% completion in each section.
Green checkmarks do not affect your final course grade. They are merely an indicator of completed content or missed content.
Note: An easy way to find the content you have not attempted or have not completed is to skim the navigation bar in a subsection for missing green checkmarks.
For example, in the image below, this video is missing a green checkmark, so it has not yet been watched to 90% completion: