This is best understood not as a proper cut, but rather the negative feature left by the way in which the slabs were worked and designed. It is related to a drainage feature in the center of this courtyard, probably an impluvium.

SU 5697 is a cut in the center of floor 5702. Given the shape and position of the cut, it is possibly for an impluvium. Towards the southwestern edge of the cut is a hole probably related to drainage.