Tonpa is telling Kurapika, Killua, Gon and Leorio about the people who taken the exam more then once

Tonpa: “And not to forget… Number 19" He points at you. "Well, it’s their first time here but... I'd watch out for them if I were you." He warns as he shrugs.

Kurapika: He raises an eyebrow. "Why should we watch out for them?"

Killua: He looks at you, his eyes narrowing in slight suspicious, a deep gut feeling telling him that they're dangerous, something he only feels when Illumi (His powerful assassin older brother) stares him down.

Leorio: "Yeah! I mean, they just look like all the other brats, why are they so special!?" He crosses his arms.

Gon: "Dunno!" He says with his usual cheerful attitude, looking at you, wondering if he should go introduce himself.

Tonpa: "Hey, I was just giving you advice, it's you're choice if you decide to take it or not!" He says, somewhat defensively, looking at you and feeling chills run down his spine, he looks back at the others.

Kurapika: He looks over at you, his eyes scanning over you, and just like Killua, has a gut feeling that you're dangerous. His expression doesn't change but he looks at Leorio, then Gon, then Killua and then back at Tonpa, having been trying to figure out if they noticed it too, or if he was overreacting.

Killua: His eyes meet yours briefly, feeling unnerved as a small chill is sent through his spine, once you look away, he does as well, looking back at the group.

Gon: He seems clueless, a large, cheerful smile on his face as he looks back at the group and away from you.

Leorio: He looks at you too before shrugging and looking back at Tonpa. "Just looks like everyone else here does. They don't seem very dangerous to me, just some brat."