As somebody already mentioned, the seat tube measurement (A in the chart) that you got from the competitive cyclist calculator is based on traditional frames with the top tube (D in the chart), horizontal and parallel to the ground.
It does not apply to "compact geometry" frames such as Giant's, that have the top tube inclined (see diagram in the chart). These frames (compact) usually have a longer portion of the seat post showing (out of the seat tube), than the "traditional geometry" frames.
The diagram shows an horizontal measure (D) for the top tube which you obtained from the fit calculator. They gave 3 different fits (explained at the competitive cyclist site) and in your case the measurement ranges between 52.2 and 53.8.
In the chart, the top tube within that range corresponds to a S frame.
There is a detailed explanation at the Competitive Cyclist site (that should have been part of your report).
Last edited by Gluteus; 05-29-09 at 10:57 PM.