The concept of percentile is different from percentage. Suppose the highest marks recieved by a candidate is 285 out of 300 so 285 will be considered as the base percentile which means 100 percentile. This means that even though the person have not scores 100 per cent marks that means total marks 300 still he got 100 percentile. So, it depends on the highest marks gained in an exam to make a percentile.