(1) The maximum population of any building or any portion thereof, for which an exit-way is required to serve shall be the maximum number of persons actually occupying such building or portion thereof at any time:

Provided that such maximum population shall, in any event, be deemed to be less than the sum of the population figures obtained by diving the gross floor area of each occupancy-unit or portion thereof, in such building or portion thereof, by the appropriate figure in Table XIII.

(2) Where an occupancy-unit is used at different times for different occupancies, the population of such unit shall be calculated for that occupancy which gives the greatest population.

(3) The population served by a stairway or stairways forming a component or components of an exit-way, and serving not more than five storeys of a building above finished ground-level, shall be deemed to be the population of any two adjoining storeys having the greatest aggregate population.

(4) The population served by such stairway or stairways serving not less than six and not more than eight storeys of a building above finished ground-level shall be 25 per centum greater than the population calculated in accordance with the provisions of subsection (3).

TABLE XIII
POPULATION DEEMED TO BE SERVED BY AN EXIT-WAY

(5) The population served by such stairway or stairways serving more than eight storeys above finished ground-level shall be 50 per centum greater than the population calculated in accordance with the provisions of subsection (3).