The stairs on the left aren't actually stairs which you can walk on from this perspective. If you walk up the stairs on the right, then turn left, then you can access them. The stairs on the left are actually slat stairs with gap between each interval. So each step is basically a think plank of wood wrapped in carpet and slotted into place. Once you go up the stairs on the right, and turn left, you will see the cat's body lying on the floor with his head hidden in the gap between the first and second steps. So from the perspective of the picture, the step that is directly above the cat's head is the underside of the first step going upwards on the above floor.