Remember that the tasks per day on each row are an average of the last few rows, and not the tasks per day of that row. That's why, for example, when there's a sudden burst of activity like on April 18th, the average remains high for a few rows. And then suddenly drops later on, once the day with a lot of tasks done drops out of the range for the average.
Also, I've excluded the columns for the total planning, as that's done and thus had no change over time.
Finally, the last block of columns, the ones in green, are just the sum of tasks of the other metrics, not something that's on the devs' reports.