Bug: Scale bar length doesn't change when you change the axis interval.

Prism (since version 4) lets you hide the graph axes, and show scale bars instead. Choose this in the first tab of the Format Axis dialog. Choose to hide axes and show scale bar(s). The length of the scale bar will be determined by the Interval set on the X or Y axis tab of the Format Axis dialog. 

If you later change the Interval (which requires first turning off the automatic range), the scale bar length should change. There is a bug in 6.0a and 6.0b (Mac) so the scale bar length is stuck. To work around this bug, go back to the first tab of Format Axes and show the axes again. Then set the Interval, and cick Apply so the graph changes. Then go back to the first tab and hide the axis or axes and show the scale bar again. It will be the length that you set for interval. 

We'll fix in release 6.0c.