звучит неплохо

REALLY here doesn't mean хорошо, it means вообще, на самом деле.

"The Russian delegates were so impressed when I greeted them with привет! They had no idea that it's the only Russian word I really know."

окей, спасибо! учту :)

Я не понимаю ваш вопрос. Это означает, что она НА САМОМ ДЕЛЕ/В КОНЦЕ КОНЦОВ на знала других девиц его возраста.

But did I understand correctly? Jane is good known by Bill's mother? Other than Bill's mother is sure that Jane is his age-mate?
Maybe stupid question, but why not :)

I tried to translate :)

So, it means, that Bill's mother knew Jane was the only girl of Bill's age?

Sorry, I still don’t understand. She knew about the girls age, she didn’t necessarily personally know the girl.

Oh, I just thought, because of "she really knew" position in this sentense, that maybe Jane was both his age-mate and his mother's acquaintance. Second thought was, that his mother just was sure about girl's age :)
Just try to understand.

Yes, she’s sure about the girls age and know OF her, but doesn’t necessarily know HER.

Okey, big thanks!