If on a given day, for example March 5, you only make 3,000 steps, then that stage is simply not completed. On March 6, however, your task is to make 6,000 steps, and on March 7 it is 7,000 steps.
If you do not publish a report at all on March 5 and March 6, but on March 7 you make more than 7,000 steps, then everything is fine — you are still in the game.
As for the form: on the website, in the top-left corner, you can choose the language. Below that there is a section called “March Form.” There you only need to fill in three things.
First, select that you are the one submitting the data — I added your nickname there.
Then fill in which day and which stage the information is for.
Finally, mark whether the stage was completed, not completed, or no data / no stage.
If you select no data, it simply means that the stage is also considered not completed.