This chapter really describes what had happened in the Don Giovanni in more detail than the poem itself. It was much better because other than the fact that we have to rely somewhat on what the patient says concerning those events (in which she described most of the time in a sexual way), we see in this chapter the events that had happened and all the odd circumstances. The use of figurative language, metaphors, similes and description tells of what was going on at the time, and the use of the first person perspective on the postcards helped understand what was going through some of the people's minds when events were taking place.
Including all this made the story about the Don Giovanni much easier to understand and also it cleared up the areas where you would think was unlcear and confusing. Not only that, but it also gives us insights about the characters and what they thought about what was happening and its importance.