SU 6143 seems to delineate two spaces, the road and the area north of the road. It is possible that it is a threshold, the presence of a tile under the westernmost block indicates an attempt to level the blocks. SU 6143 also appears to be aligned with SU 6168, which could indicate that the SUs extended at some point in time.
Western portion of Room G-1
SU 6161, SU 6143, SU 6164. Taken from north.
SU 6161, SU 6094, SU 6164, SU 6143. Taken from south.
Photo from north