Seth really doesn't know Daniel well enough to reassure him verbally, but it still pains him to see Daniel sad. He doesn't know how it happened, how this guy somehow elicits this reaction so easily in him and why Seth is so convinced he needs and deserves Seth's attention and compassion.

But he is convinced, and he wants to give it, so he leans forward a little to sit properly next to Daniel, and rests his hand on his back in a way he hopes is comforting. He just... wants Daniel to know there is someone there who actually gives a shit.