I know see https://groups.google.com/forum/?hl=fr#!topic/re3-dev/F55YjZi6nDw ,  I'm waiting an answer.

Magic value are INCHES_PER_UNIT and DOTS_PER_UNIT found in  OpenLayers 2 https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Util.js