Level of mock series to appear for cka

How much one should score in mock series to qualify CKA?
Are the questions tough than the exam ones? Or they are organised this way to practice better and prepare for any harder.

They cover some things that you won’t see on the exam, but in general, it might be a little harder than the exam. Still, you should be getting fairly high scores in the Ultimate Mock Exams – near perfect score, taking considerably less than full time to finish an exam. If you’re getting low scores or running out of time, you definitely need more practice.