Those domains can be caught from Pool, snap, or NJ. If you check NJ's FAQ, it is written that if you want a domain so much, then bid more than minimum.
If you bid minimum at NJ and another domainer bid at Pool. Then, you will have %50(fewer or more that depends) chance to get that domain caught by NJ. But, if you bid "minimum + some amount" instead of minimum, than NJ take it more seriously and the chance to get that domain caught by NJ will be %(50 + x), where x>0.