The scale of a bar graph is the range of values presented along either the horizontal or vertical axis. The interval is the smallest quantity between two tick marks along an axis.
For a vertical bar graph, the scale for the vertical axis usually begins at zero and goes up to above the maximum data point. However, the scale does not have to start at zero. For instance, the sales figures for a company in October, November and December are $77, $78 and $82 respectively. If the vertical scale is from zero to 90 with an interval of 10, the difference in sales between the months is hardly noticeable. However, if the scale is from 74 to 85 with an interval of 2, the difference in sales between the months becomes very noticeable.