[With Sans as a brother, it's not as though Papyrus is unaccustomed to people not matching his tone even when he's upset. Not with how Sans almost never acknowledges serious situations for as serious as they are, when he's around. Maybe her tone isn't the warmest right now, but the words more than make up for it.]

That's... good. That's good.

[He gasps a little as he speaks, trying not to breathe so deeply that it puts even more pain on his sides. Another hiss, because as cramped and uncomfortable as the cell is, now he can't seem to find a position that doesn't hurt.]

Thank you, I'll... uh, try to return the favor. Maybe... I'll reread that first aid book...