When Chen Fan talked about the Grandmaster, Lei Qianjue and the Dark Roll, people such as Chen Zhenxin only have a very vague idea of what they were but couldn't gauge exactly how powerful they were since they sounded too far removed from reality. Some people even doubted Chen Fan was telling them the truth.
However, when Chen Fan told them that he had defeated the entire fourteenth brigade and struck down seventeen airplanes, they simply couldn't wrap their minds around it.
Unlike a Grandmaster, they knew what the army was and knew that they were extremely deadly. No individual could have survived a fight against modern killing machines.
Therefore, Even Chen Huaian and Wang Xiaoyun found Chen Fan's story inconceivable.