The floors are the specific diaphragms at specific elevations so the buildable areas for each floor (figures 10-12 of the design guide) are showing the buildable areas (extents) of the diaphragms.  This lacks information about the buildable volumes above each floor.  The buildable areas of the diaphragms in figures 10-12 are still consistent with the diaphragm shapes in figure 13 (each line immediately below "f = #" in figure 13 represents the floor diaphragm in figures 10-12).  Figure 13 also shows the buildable volumes above each floor.  In the case of floor 10, the buildable area of the diaphragm (12in x 12in) is not the same as the buildable volume above the floor (5.5in x 5.5in).
Rentable floor areas are derived from the buildable area of the diaphragm.  So the rentable floor areas are also what's shown in figures 10-12 of the design guide (the floor 10 terrace area could be rented out as a dining area or something).  The bottom of the atrium (floor 1, 6in x 6in center area) is not considered rentable floor area, but the bottom of the terrace (floor 10, full 12in x 12in) is considered rentable floor area.