costycnc how inkscape create svg in mm

 My page is www.costycnc.it ... and my id is costycnc ... so ... try on internet costycnc .

I create this page www.costycnc.it/cm8 for transform a image to gcode , i modified potrace https://kilobtye.github.io/potrace/ for transform coordonate to gcode ... practicall all lines that compound svg i transform to gcode ... for example L 10 10 to G01 X10 Y10 (at line 1249)... C 10 10 to G01 X10 X10  (at line 1239)  see here https://www.costycnc.it/potrace/potrace.js.highlight.html#1236

Inkscape create document svg with height and with in mm ... my old transformed potrace to gcode ... create a gcode in mm but svg in pixels ... so now i try to  produce also the svg file in mm not in pixel.

The dpi of my system is 96 (also the inkscape use 96 dpi ) so the old svg produce 378 for 10 mm ... so I did not understand because this 378  ... but here explain better 

https://stackoverflow.com/questions/35517230/lines-look-irregular-in-thickness-when-using-texturebrush

Since the convention is that all monitors have 96 pixels per inch, and by definition 1 inch == 25.4 mm, we have that 0.1 mm == 0.1 mm * 96 (px / inch) * (1 inch / 25.4 mm) == 0.378 pixels (approximately).

so ...here   https://www.costycnc.it/potrace/potrace.highlight.html#155 at line 155 i put 100/378 for result values in mm ... first was 1 and svg measure result was in pixels...

now need to understand better to finished program!