A member of the Nights Watch states: Let them die. Less enemies for us. Under his breath, Stannis mutters: Fewer. He doesnt expand on this when Davos questions what he said, as it was enough for him to correct the grammar to himself. Yes, even with wars going on, people dying, and the impending threat of White Walkers, Stannis still recognises the importance of proper grammar. It isnt the first time this has happened either, as back in season 2 he made the same correction to Davos, when the Onion Knight was discussing his missing fingertips (clearly he didnt remember the English lesson). All hail Stannis Baratheon, Lord of Pedantry, the One True King of Grammar!