EXCITED about his purchase of a $2 million, 67th-floor apartment at the AOL Time Warner Center on Columbus Circle, the buyer decided to sit in Central Park on a spring afternoon and count the floors. ''It was presented as an 80-story building,'' said the homeowner, a marketing executive for an international company, who spoke on condition of anonymity. ''I kept counting and coming up with 69 floors. If I'm right, I'm 13 floors lower. I'd be on 56. That's terribly disappointing.''

While the practice of misnumbering floors in some of the city's most opulent buildings has been going on for some time -- starting, of course, with omitting the 13th floor to appease the superstitious -- the sleight of hand has become more blatant with the arrival of Trump World Tower, opposite the United Nations, and the double towers being developed by the Related Companies for the AOL Time Warner complex, projects whose sex appeal and marketability turn, at least in part, on their soaring height.

''Donald Trump is the father of this,'' said Richard Wallgren, director of sales at the AOL building, which will be ready for occupancy this fall. ''He'd say, 'This building has 75 stories.' Of course, when you counted, they were missing 10 stories because he gave the lobby 15 stories or something, and apartments would start on 16.''

AOL explains the new calculus like this: if they use the average height of a ceiling in New York, 8 feet 8 inches, as their standard, the AOL towers, which were recently topped off at 750 feet each, could be counted as having 80 floors, even if they do not. (The apartments at the AOL tower have ceilings that are 10 feet or higher, so there are fewer actual floors.)