I think he lowered his demands to 6x6 the last time he spoke with the Rangers. Too much money IMO.
I believe the lowest he ever got was 6.3m. But he also wanted a full no trade with that as well.
Callahan will probably go lower unless somebody throws stupid money at him. In Florida he could take a contract that was technically significantly less than what the Rangers were offering but still walk away with more money at the end of the day because of the lack of taxes.