How did Ye Weiming know?
Of course, he guessed!
But not just any guess, it was an educated guess based on rational inference.
The core of the task was "18 Dragon-Subduing Palms", even the name was "Dragon's Might", so he inferred the task should most likely be related to "18 Dragon-Subduing Palms".
Besides, the one who offered the reward was Old Beggar Hong Qi, which further confirmed his speculation.
If not guiding him in the use of the "Dormant Dragon, Beware", could Hong Qi pass him another stroke from "18 Dragon-Subduing Palms"?
If so, Ye Weiming wouldn't mind at all.
He swore on it!
Hence, in order to maximize the reward, Ye Weiming upgraded the "Dormant Dragon, Beware" to an unmovable level before Old Beggar Hong Qi announced the reward.
His maneuver, however, frustrated Old Beggar Hong Qi.