He's actually thrown off when she blurts out that request, partially because he didn't expect it at all and...also partially because it wasn't exactly where he was going with this. But...he can adjust, he can go with this as a start.
He lets out a long breath and sits on the edge of the bed, leaning over his knees. "Um-- yeah." he nods, "I can explain it...but no," he shakes his head, "it's... not slang or anything. And...it's complicated." How many times has he said that recently? Everything is always complicated.