The preparatory work for an assignment should be documented here, in the coursework section.
The separate categories Assignment 1, Assignment 2, Assignment 3 and so on, are for the formal hand-in presentation notes that you will send to your tutor, tutor reports, and any follow-up work you may do responding to feedback from your tutor.
Log entries for specific projects (or exercises) should make it clear which particular project they refer to. You should also include photos both of your work and sketch book pages.
You also need to make a clear reference between the relevent blog posts and physical pieces of work that you send to your tutor as part of an assignment – and also when you send in your work for assessment.