I understand that. The point Underhill made was that they did not think he was worth the number that he would get on the open market or via franchise tag, and they were not going to pay him that even if they could (which they potentially could have by letting M Williams go), because they didn’t think he was worth it.
Again though this isn’t me saying this, it came from Underhill, if you want to hear exactly what he said I recommend checking out their postgame podcast from last week.