During the export process, you can choose the scale for which your work will export to. Use this to match your or your clients scale requirements or just use the default Fit to Paper.
As shown below, how your work will appear based on the combination of settings selected (including this output scale) will be shown in the preview to the right.
Create your Own Specific Scale
At the bottom of the list of preset scales is an option to Create New Scale. Tap that option and define. Once defined, the new scale will always appear in the list of presets.