Well if you understand sufficient and necessary language then I don't know why your confused about the second statement getting reversed. The second one starts with Only that's why G is on the necessary part. As I have explained, Only indicates necessary.

I am worried when you say "I understand which words indicate sufficent and necessary" but your question wouldn't be posted if you really did. As I have mentioned in the first post, I would highly recommend reviewing your sufficient and necessary language.