What does the underlined sentence mean?

Reading Comprehension: Read the quoted parts carefully and answer the questions in English. Write your answers in the corresponding space. “Who is he” I demanded. “Do you know?”“He's just a man named Gatsby.” “Where is he from, I mean? And what does he do?” “"Now you're started on the subject,” she answered with a wan smile. “Well, he told me once he was an Oxford man.” A dim background started to take shape behind him, but at her next remark it faded away. “However, I don't believe it.” “Why not?” “I don't know,” she insisted, “I just don't think he went there.” 
What does the underlined sentence mean?
【正确答案】：

PEOPLE BEGAN TO KNOW SOMETHING ABOUT HIS BACKGROUND,BUT THE FOLLOWING CONVERSATION INDICATED THAT HIS BACKGROUND INFORMATION WAS FALSE.

【题目解析】：划线部分意味着人们开始对盖茨比的背景有所了解，但是下面的对话表明他的背景信息是假的。