The range is a measure of the variability in a set of scores. To calculate the range, you need to find the difference between each score and its mean, then take the absolute value and square it.
The larger this number gets, the more different each score is from one another. The range is calculated by taking the absolute value of each score and squaring it. This number gets larger as more scores are further from one another, or when the variance between two groups increases.
The most common use for this measure is to look at what a given probability distribution looks like in order to understand whether there are any extreme outliers that would skew an interpretation of a data set.
Sample size can have different ranges depending on how variable their scores are. For example, if you had 16 people who scored 50 points on an exam with a mean of 75, then all but two subjects outscored everyone else (and thus have lower than average variances).