These small ashlar blocks forming a rectangular space in the northeast corner of room G-10 seem to post-date the first phase in this room since they cover the wall facing against wall 6133 in the north (and presumably the marble which used that facing was already spoliated at the construction of the eastern section). It may be related to the feature that has been spoliated to the south. Further excavation of layer 6276 may help clarify this.
Photo from west
Room G-10