The Step 2 CS has no numerical score. You earn a "pass" or a "fail" based on your ability to gather data, communicate with the patient and write an effective report.
On all other parts of the test, the number of correct answers you earn is converted into two numerical scores, one on a three–digit scale and the other on a two–digit scale. These are simply two ways of reporting the same result to schools. You must earn a 75 on the two–digit scale to pass.
While your medical school education will give you many of the skills and much of the knowledge necessary to pass the USMLE, you are still likely to log a substantial amount of time reviewing and preparing for each stage of the test.