An Assignment can exist in different Modules. :For example, let's say that "Assignment A" will take two weeks. The instructor could put Assignment A in both the Week 1 and Week 2 Modules. It's just ONE ASSIGNMENT that appears in two different places. Therefore, if the instructor is in the Week 1 Module and makes a change to "Assignment A," that change will appear in the Week 2 Module. Again, it's just one assignment.
Now, some instructors want students to do multiple assignments that follow the same format (e.g. Week 1 Reading Log, Week 2 Reading Log, Week 3 Reading Log.....) These will be DIFFERENT ASSIGNMENTS. Yes, they will follow the same format, but the Week 1 Reading Log will be housed in the Week 1 Module; the Week 2 Reading Log in the Week 2 Module, and so on. Making a change to the Week 1 Reading Log will not affect the Week 2 Reading Log because these are different assignments.
If you want to set up multiple assignments that follow the same format, create your Week 1 Reading Log. Then duplicate the Week 1 Reading Log, but rename the new one the "Week 2 Reading Log." Now you will have two separate assignments.