I'm pretty sure it aligns your raw mark up. My teacher said if you get anything above 80 raw then you're looking at a band 6.
Edit: She meant 80 raw in the trials though...only 3 people got above 80 at my school.
err...you have to write about your PRESCRIBED text which is obviously about journeys and related texts which are also related to journeys. Although you could possibly adapted those texts from your change essay....its impossible to actually write your change essay.