You know, I couldn't find this damned table for some time (after being told to go look at it), because it's on page *5*!  Page 5 is for installing instructions, and "what this first menu means" kind of stuff.  
 
Anyway, it explains right there that a 6 is not just rerolled and added.  You subtract one, and reroll.  So there is no statistical variation in odds between 5, 6, 7 etc.  I roll of 5 is 5.  A roll of 6 is 5 + (d6).  So your odds of success are not affected by the DRN mechanics.
But Endo, it's not a 0-5.  It's 1-5, with each roll of 6 simply being another 1-5 on top of that.  0 would just suck.  
