Looking at the jade slip, some of the people recognizes it as they're in the proximity when Wu Xiaotian was refining it, astonishing them as the immortal-like young man refined the jade slip at an extremely fast speed, making them wonder about the authenticity of the young man's claim.
They don't have the guts whether it's real or not though as they already saw and is scared of what Wu Xiaotian could do to them just with his soul power alone, hence they decided to just stay put and watch for now, thinking that it will eventually be revealed whether the jade slip could really achieve such effect once demonstrated.
Sensing those doubtful gaze, Wu Xiaotian continues explaining the purpose of the jade slip, each sentence coming out of his mouth making those interested more and more wide eyed.