Mentis started to grip the front of his oversize coat, a nervous habit of his. The idea of calling her by her first name, not by rank or even by her last name, it wasn't something he was use too, and so he seemed to become even more anxious than before. He lifted his gaze back up to her, so not to be rude about, and so that she could hear his quiet voice.

"Oh, sorry, Yes Ms lieute-...I mean, Yes Ms Arya" He smiled to her again, He always seemed to smile at everyone, even if it was out of nervousness
"I will just be over here, if you need me" 
he mumbled as he stepped to the side while gesturing to the spot he would stand, out of the way of all the others, no doubt they were already judging him. And why wouldn't they? they were here to fight, and he couldn't even stand to touch a gun, let alone lift one. When he got the opportunity to the find infirmary on the ship, he could stop being so nervous about everything.
While waiting for the orders, he took this moment to examine the other six members. Days before coming here, he pulled up everyone's medical records, well as many as he could get his skinny fingers on. So despite not really knowing anyone on the team, he at least knew who they were and what they were.
He had noticed the two who arrived a little after he, the one who emerged from the shadows, and the other under the cloak, who seemed to be rather flustered as she reported into the lieutenant-major. She seemed worse than he was at talking to people, but that is a rude thought, and he shouldn't think like that again.

When Arya started to speak to them all, Mentis turned his gaze onto her, listening closely so not to miss anything, it wouldn't do if he missed important information because he wasn't paying attention. Though it seemed only to be a summary of why there were here, important mission debriefing would probably happen once they were all settled onto the ship. 
Mentis frowned slightly though at the 'awarded handsomely' part, no one just did this out of the goodness of their heart, there would always be an award, though maybe he could just give it to someone else, whatever the reward would be, or just not request one. He didn't like making a big deal out of things, he was only there to help the people and his new team the best he could.