Wherever a regulation is applied herein to any R district, it shall be understood to apply to any district designated in Section 17.02.060 by the primary symbol “R” and shall be understood to apply to any PD district if that district contains any residential uses. The regulation of secondary housing units in certain residential districts shall be understood to apply to any PD district if that district contains any residential uses. Wherever a regulation is applied herein to any C district it shall be understood to apply to any district designated in Section 17.02.060 by the primary symbol H or C. Whenever a regulation is applied herein to any M district it shall be understood to apply to any district designated in Section 17.02.060 by the primary symbol “M.” (Prior gen. code § 8-19.6)