When she moves, Severus makes an almost imperceptible motion - not a flinch so much as a leaning away. His fingers tighten around his wand as though he expects an attack.

And with her words, it thus becomes unnecessary to introduce himself to Stephanie; he glances at her and gives a slight tilt of his head, an action which exudes more wryness and irritation than manners. With that, he directs his attention to analysing the situation. When is Burbage from? Not her death, clearly - not if she's looking to him to answer her questions. Some time before, then. In that case, he feel safe asking, "What do you remember?"