The Ortelius scale bar is dynamic based on the ratio of drawing units (for example, cm) to scale units (for example, km) in the drawing /scale setup. To have the units represented in even increments on the scale bar, the scale units must be set accordingly. So, you may have 8.23cm = 10km as your scale and the scale bar will represent in 10km increments (or smaller, for example, if the scale bar is too short it will automatically adjust to show in increments of 5). Drag the bounding box of the scale bar to see how the increments adjust based on the room available. It is not possible for the Ortelius scale bar tool to be set to a constant number – it is always tied to the map scale. Since Ortelius has a full suite of standard drawing tools, it is possible to draw your own scale bar with drawing tools.