Here the x axis is days since the course opened, and the figure shows the total number of submissions (counting only one submission per student per task). The total number of submissions was 2728. Blue — when the students submitted their latest solution. Black — earlier correct solutions. The black lines indicate the task deadlines, and the gray lines are the starting and ending days of the course.
The plots are based on data loaded on 2022-08-08 at 09:00.