Sam had noticed the bites and scratches on the other mans arm, he just figured maybe he'd shown up in Marrowood like that. I mean, the guy was wearing armour, it wasn't exactly a leap to assume he could've been fighting before he got here.
"Man, from everything people have told me about the place, I wouldn't be underestimating anything here, even if it seems too small to bother with."
Then he realised the words Hawke had used. 'Dragon sized.' That sort of implied he knew what size dragons were. "Hold up, you have dragons where you come from? like straight up fire breathing lizard type dragons?"