The answer to that really depends on how confident you feel. I look at the scores and I think they are good. But do you feel that you can do your best in the exam? There's no need to score 100% on the quizzes. As long as you have a broad and solid understanding of the concepts in the exam content outline, and have enough exam practice to feel that you can manage your time etc, then that's the time to book your exam if you have not already done so.