Most employers don't pay only one rate to all the jobs in the same pay grade. For instance, an employee having a longer tenure in the company can’t get paid at the same rate as a beginner = in spite of being in the same pay grade.
Therefore, vertical pay ranges are formed under each pay grade. These are depicted as vertical boxes against each pay range, depicting the maximum, minimum and midpoint pay ranges for each grade. It is also sometimes depicted in a tabular form against each grade.