Ivana,
It's unclear from your question as if you're using the Prepcast (a video guided lecture) or the exam simulator.
if you're using the exam simulator, if you want to get questions in a certain domain or knowledge area, choose that doman/knowledge area for a "quiz" of 50 or so questions. At 50+ questions, it should give you a good smattering of the questions in the area.
Do try to get through all 1600+ questions though in the exam bank.
Harry