ming_setscale() sets the scale of the output SWF.
Inside the SWF file, coordinates are measured in TWIPS, rather than PIXELS. There are 20 TWIPS in 1 pixel.
Originally, Ming used the TWIP coordinate values, but this was quite often confusing, especially when loading a Ming generated movie into one created using Flash.
Ming v0.1.0 addressed this, by making the default coordinate system use Pixels. This function is to allow older code (which assumes the scale to be in TWIPS) to continue to function as it did under Ming pre 0.1.0
As the Ming site says, "If you have no idea what I'm talking about, good. " Because you then have no need for this function.