I agree with Brad and Diva.
I would take a 90 question practice exam on exam masters after each organ system and I would score between 60-65%. It made me nervous also, because I felt like I wasnt performing well enough on the practice exams to pass the PANCE. I can reassure you that exam masters is harder than the actual PANCE. The questions on exam masters are longer and more in depth than the questions on the PANCE, so if ur scoring in the 60's I wouldnt be too worried.
Hope this eases ur nerves a little ;).
Good luck on ur exam.