Completeness (as a percentage) of symmetry-unique
               anomalous difference data within the intersection of
               (1) a sphere (defined by the diffraction limits,
               _reflns.d_resolution_high and _reflns.d_resolution_low)
               and (2) the ellipsoid (described by
               __reflns.pdbx_aniso_diffraction_limit_* items),
               relative to all possible symmetry-unique anomalous
               difference data within that intersection.