Odds are he has agreed to take below slot money, hence why he was picked that high. Still gets paid more than what he would've gotten at his 'projected' spot and club has more to attract players that demand above slot $$ to sign. These are either HS players or college players who have eligibility left and have some leverage.
For Carson and players like him, he could say no, but then has zero leverage next season and unless he puts up monster numbers, probably doesn't improve his draft position.