Just wondering how much your little ones eat per meal/day?

My MIL watched my son yesterday and said he didn't much while he was with her, he only had blah blah and blah. I said it sounded fine and I'd just give him a small snack when we got home and she made a comment about how he must be constantly hungry if I think that's enough. He's gaining weight steadily and whenever he stops eating we ok wait a few minutes before trying to continue just to make sure he's full and if he is then we don't try to force more food on him but now it's got me thinking and worrying that my baby is going hungry 😒