Frank doesn't understand the look, doesn't understand what they are telling each other... but he does see when two people are having a silent conversation. Percy and Annabeth shared a lot of those, when they finally got reunited- they were honestly like one most of the time. He guesses that happens when you fight with someone for so long. Frank had fought with Percy, yes, but he was still kind of a newbie when it came to quests. He knew how to work in a team, he knew how to lead because it was in his blood- but he honestly lacked the experience.

"It's Frank. And I will be alright when we go inside and know what we'll be facing." And then, with a grin as he pulls his bow closer to himself. "Good luck inside. Those are really cool weapons, by the way."