If I remember correctly the depth map is converted to signed ints for convienence - I don't remember their min or max values .. I don't think I used SimpleOpenNI (middle middle) software before either - so don't know if they put on any parts :P

But what I DO know is that this should be improved.

Where you click in the depth map is ready to do "something" - what it should probably do is report the depth raw & translated value.  Might be nice to have a min / max too but depends on interest...