When you include a map in a text of yours, usually you can scale the graphics to fit your needs. The exact procedure depends on the program you use of course. Such additional scaling is helpful, but actually it should be superfluous since PP3 can deliver the map with the desired size.
set box_width 10 set box_height 5
set the width of the map to 15cm and the height to 10cm. (By the way, all dimensions are given in centimetres in PP3.) The only thing that's still missing is the scale of the map. It is set with
set grad_per_cm 6
which sets it to 6 degrees per centimetre. With the current projection method1, the given scale is only exactly true for the centre of the map. Towards the rim there is a slight magnification (and distortion).
 the equidistant azimuthal projection