This addendum corrects the definition of the internal change-vector components used in the main SCG paper and in Addenda 1–3. The original manuscript restricted each component of the change-vector to a non-negative range, but the geometry developed throughout the paper and subsequent addenda requires a symmetric range that includes both positive and negative values. Each component of the change-vector represents a directional contribution of internal change along its corresponding imaginary axis, and therefore must be allowed to take either sign. This symmetry is essential for describing curvature orientation, geometric asymmetries, and internal rotational behavior. The boundary case corresponds naturally to the photon-like limit, where internal change becomes fully imaginary. This correction ensures consistency across all earlier SCG materials.