The entrance door to a multi-floor dwelling unit in a Group R-1 or Group R-2 building or occupancy shall be identified on the door jamb on the public corridor side of the door by an approved fire emergency marking, not more than 12 inches (305 mm) from the bottom of the door, indicating the dwelling unit number and/or letter. In addition, every door of each such multi-floor dwelling unit that opens to a public corridor or other means of egress shall be identified on the public corridor side of the door by one or more upward or downward-pointing arrows indicating the direction(s) of the other floor(s) to which the multi-floor dwelling unit is connected.