With a full 15 minutes per beer, you should have no difficulty Completely filling the exam score sheet, and I wish more BJCP judges took this seriously on competition sheets as well.  On the exam, ensure that you address every cue word on the score sheet, and also verify that you Completed all the required Feedback on what you Perceived/Described as lacking.  Between addressing any obvious flaws, fully describing the beer using all the provided cue words, and also stating how the beer could better fit the style, you should completely fill the sheet and leave no blank lines.  With attention to detail, there is no reason you cannot get full credit on this aspect.