This mistress was not interested in her slave's explanation of what had happened. All she knew was that she had given him a task which he had failed to deliver. And in her book, once you do not deliver, you have to face the consequences of failure. The consequens for him were being trampled and crushed with shit filled boots. She had stomped on cow dung and she had her slave lick her boots clean.
When she realized that her slave was not going to do what she had asked him to do, this mistress immediately took out her boots and she wore then. She could not believe that her slave could disobey a direct order. So she used her boots to trample him and crush him. She forced him to lick the dirty soles of her boots and by the time he was done, he had learned his lesson.