KBB, NADA or Edmunds?
The NADA price is a retail price, i.e. the price you would expect to pay at a dealer. The other prices are prices for sales from a private individual. You pay more if you buy the same car at a dealer, so that price is higher. You don’t have to pay the asking price and the seller probably doesn’t expect that you will. Make an offer that you are comfortable with that is somewhere near the two lower values. If you want to haggle, then start even lower. Provide the seller with copies of the KBB and Edmunds estimates.