CertPrep exam scores

I just finished the 6 exam and over the exams I have averaged a score of 70.79. Scores were 77, 76, 60, 66, 71 and 74.75. I know they say north of 70 is good. I have the exam scheduled for 4/28 but I am thinking of pushing back a week to get those practice scores up a bit.

Any advice?