The way she says his name (that name) has his eyebrows raising in surprise, and then mild incredulity.

"I'm fine." Truthful, not defensive. He hasn't felt anything yet. If there's any truth at all to what they'd been told, then it seems clear he still has time to figure it out. And he's still hoping to never need to figure it out, considering the only people here who he'd be willing to tether to are Rey, who can't help with the imbalance issue, and Vader, who could, but seems to have all of Kylo's skepticism and perhaps more.