Over time the concept of eating till you're full will change, you eat till you're not hungry anymore is more the idea. And it will take you a while to trust your body on that, at the moment, you probably dont recognise the feeling and feel like you've just having to pick an arbitrary spot at which to stop.
I have trouble with this too still after 18 months. I bought a salad for lunch today and it was huge, and I'm eating my way through it. My head was STILL even after this long saying finish it, finish it. I wasnt getting *full* I just stopped half way through, put it aside and after five minutes realised I didnt need anymore. Its something I think we all always have to work on and remain attentive to.
I can eat a sandwich - a small one, like a grilled cheese sandwich, not a huge massive salad and ham sandwich, but that's unusual at my stage, and there's plenty that will scream ALARM ALARM your band is slipped, you have a stretched pouch but some people can continue to eat larger amounts than others. I tend to be one of them but thankfully I can also lose weight on a higher calorie level than many others.
Its SO individual - you really cannot listen to other people or go by their experiences with this. After one fill, its not at all alarming to be able to eat that and I also think its quite dysfunctional to get all caught up with what you *should* be able to eat (or should not be able to eat!). You eat till you're not hungry, whatever amount that is and if you're losing weight, its the right amount, whatever amount it is.