What does it mean to turn spare ink into clouds and smoke?

The empty pen and ink turned into clouds and smoke

This poem comes from Ouyang Xuan's "Li Bai's Post on the Balcony" "The young master of the Tang Dynasty has been a fairy in brocade robes, and his literary talent has been popular for six hundred years. No beams can be seen." The bright moon shines, and the spare ink turns into clouds and smoke."

Ouyang Xuan, a calligrapher of the Yuan Dynasty, wrote this poem after seeing the "Tie on the Upper Balcony" written by the poet Li Bai.