When you start a new map, the New Drawing Wizard looks for certain map notes attached to the template.
The map note called Resize lets the New Drawing Wizard know how the template can be resized to match the dimensions typed by the user. The possible options are:
If you map can be scaled XY (eg it has a width 0 line as a border) type SCALEXY.
If your map can be scaled then stretched if necessary (eg the default cc3 template) type STRETCH.
If your map can only be scaled (ie it must keep its aspect ratio) (eg Allyn's map first in the profantasy.com/cc3 gallery) type SCALE.
If your maps is a fixed size type FIXED (so that people can create specific-sized templates eg for Traveller worlds)