He is the slowest of the three of them, and Sam had already been planning on heading back that way anyway. He's not sure he trusts Jon to actually get his butt back here anyway, especially when he's not moving at top speed, so Sam is thankful he doesn't have to argue too much more to get them both to agree.

At Coraline's comment, Sam simply salutes, because she's right to be uneasy and he already does feel better knowing that she's someone he can trust to get them through, whether Jon wants to go or not.

"I'll have him there in twenty. Scout's honor."

And then Sam is sprinting off back to the dungeons with very little else said.