That first response gets a stare of frank and understated bewilderment, almost patiently waiting for Severus to move on or explain to Lucius what the matter is. When it turns into the former, Lucius has no complaints; he listens, and sips from his wine, sort of only skimmingly invested in whatever turmoil brought him here to share a bottle of wine.

Which is different to the usual 'not at all', in fairness. "They seem to understand a great deal more than one would expect. Enough not to ask very many questions."