He'd have an easier time with those questions she doesn't ask. This general feeling of polite concern, sympathy, he's not sure what to do with. For a moment Severus just looks at her, in the space of conversation where one might say 'It's alright' or 'I've had worse', like he's an actor who's forgotten his lines. She may feel as though he's staring at her like she's suddenly grown a second head.

What are you playing at? What do you want from me? He doesn't ask because no matter how paranoid he is he isn't quite so stupid as to think there's a personal motive here. They have the same preceding numbers on their arms (his is covered, always will be, because of what else is on his arm) so they'll be housed near each other, he is now a 'familiar' face, who did her a favor. He's dug his own grave here and he's unaccustomed to doing anything besides shouting at people from the pit. At the moment he doesn't have the energy.

"That's nice of you," he says eventually, awkward.