There's a mental grunt of agreement (did anyone know that could even be a thing?) because she does make a good point. When he glances forward and away from her this time, it's thoughtful instead of avoidant.

"I just didn't know..." Anything, really, and maybe that's what is digging at him the most.

The alcohol had been new, the freedom and fun of it had been new, letting himself follow what had caught his interest because he was being mindless about it... and then that had led him into a talk that he definitely had not expected. He'd had no idea that there were implications and social clues and facets of living layered into everything going on that night. He feels stupid that he'd walked blindly into what had apparently been a minefield. He feels embarrassed that he might have given signals about himself and his intents that he hadn't meant to. And he feels mortified that he might have to consider it further.

If all of that could be summed up into vague clouds of impression, that's what he finishes his statement with in her head.