When setting the value of certain numeric properties (like "width" and "radius") you can specify either an absolute amount, or a percentage relative to the current setting.

So, for example, you can say:

    box width 2.3cm

To create a box with a width of 2.3 centimeters - an absolute amount. Or, if the current "boxwid" variable value is 2.0cm, then you could do the same by saying:

    box width 115%