If she needs clothes, Grey knows that Dawn should go to Cinna. But how does he convey that without words? He tugs lightly at what he's wearing, watching Dawn's face. Does she understand? He even mimes stitching on what he's wearing. Cinna makes clothing. If that helps her to know who he is.

Now, to the question at hand: he has to think about that. He's not great with dates, because on the train it didn't matter. But he raises one finger. One year? Perhaps a bit more. Here and in Teleios, but he doesn't even try to explain that.