@KayleneP, as I see it, last chapter it was unclear whether he was really hungry or not, but now we know that he wasn’t. So the only reason for him to place a second order (and eat half of her sandwich at that) is him being considerate
1) Notice the first few frames. She dropped the filling out of the sandwich due to surprise. So, he replaced the sandwich but had it cut to bite sized pieces so that wouldn't happen again.
2) By eating her sandwich he assumed her bill. This is assumption since it's not explicitly shown. But that probably occurred due to how sit down restaurants work. Since he ate it he would pay for it. That would be how the conversation goes when the waiter comes with the bill. And since he was the one who ordered the rest of the food he would pay for that too.
He didn't say that was his intention because, unless she brought it up, it could be passed off without causing her embarrassment.