The fact that he could not stand to shoot and shoot a ball indicates that Paul had a serious issue with his legs and this could stop him from playing the game for as long the doctor must have said.
Bouncing the basketball on the ground while sitting down shows his hands are OK but cannot be used to determine the level of injury he has on his legs because while he is bouncing the ball on the ground and sitting down makes him seem OK to the onlooker.
His writing on the cast as well shows his hands are OK but him sitting down and unable to stand to shoot a short shows he was a problem with his legs that made the doctor say he can't play for 6 weeks.
