Madame Marissa had assumed that her slave knew how to clean things. But he did not and she did not like how he did it. So she punished him so that he would associate the punishment to not cleaning things properly. She spat on the sole of her shoe and made him lick it clean. That would motivate him to do the right thing and clean things the way she wanted them to be cleaned. That worked as he cleaned them better from that day forward.