Mistress Zephy was not ok with the way this guy had wasted her time. She felt that the best way to deal with him was to make him learn his lesson by forcing him to lick her sneakers. He was then turned into a foot slave and she gagged him with her feet. He was shocked and he was scared of her. And that is how the punishment worked as intended.
This guy was an asshole and he needed to be reminded of it. Mistress Zephy did more than remind him that he was an asshole. She went out of her way to make him cry and beg her to stop torturing him. She had chosen to make him her foot slave and she had him do that until she was tired of humiliating and dominating him. He never did it again.