Looks likie they're asking for a bonus density which would increase the height to 32 floors. One ground level lobby with amenities, 8 floors of parking and 23 floors of residential units.
See attachments from
December 19, 2016 meeting of the Design Commission
Elevations:
351 ft 10" to main roof. Does not count roof screening)
Massing Models:
Renderings of base:
No rendering of the tower, but I'm guessing it looks the same as the 18 story version, only taller.