The column unlabeled on the left is that make and models advertised size. It is in mm some measure in cm (56cm, 58cm, 60cm) as in the USA. Measured in Centimeters (CM) or Millimeters (mm)The 1st unlabeled column is THEIR size (or what they call it) and usually corresponds to what they feel it most closely measures in terms of traditional frame sizing from years ago. Column 'A' is the actual seat tube and can be used as a reference point if you are between sizes and need to to figure if you should go up .5cm or down .5cm.and may help with extra data in helping determining crank length and seat post length needed (not positioning) along with 'D' (Stack) which would be similar to a traditional size number if the top tube was still horizontally level and because of this are notably very close to the first column numbers. One of the most important numbers is 'C' (Reach), as this will determine your stem length, comfort in terms or being stretched out and effect handling. I personally tend to consider 'B' as well since seat tube angles can vary from frame to frame and even though 'Reach' numbers can be the some on two different frames, with a different 'B' (Effective Top Tube Length) length they can end up feeling very different.
My best advice since you can not test ride this frame (unless you know someone that has one in your size locally) is to go to a sizing and fit website. One of the better ones that I know of is http://www.wrenchscience.com/ Create a login and go through that 'fit system' (its free) and it will ask you all kinds of question. You will need a tape measure among other things.
Yo may want to visit this information from a guy I trust that knows an awful lot about bicycles.
Articles about Bicycle Frames and Fitting
Revisionist Theory of Bicycle Sizing
If so inclined, here is some additional excellent reading on bike fit
The K.O.P.S. (Knee Over Pedal Spindle)method of bike fit
The Myth of K.O.P.S.
Debunking the Myths by Klein Bikes
How to Fit a Bicycle
The why they make frame measurement charts the way they do these day and how the industry has changed through history could easily take dozens of paragraphs. In short. When bike frames were primarily alloy tubes, they could be cut to whatever length imaginable. Typically varied 1CM or .34 inches and some manufacturers had half sizes that were differences of .5 cm or .197 inches. Top tube used to be almost always horizontally level and since there was no real standard, some manufacturers measured from the center of the crank to the top of the seat tube while others measured from the bottom of the bottom bracket to the top of the seat tube. The most widely adopted as anything close to a standard was measuring from the center of the bottom bracket to the center of the top tube.
Today more than 70% of bike frames manufactured are carbon fiber like the one you referenced. There are not as many frame sizes manufactured since CF molds are very expensive. Thus you do not see half sizes and some manufacturers even mold frame size offerings in 2cm increments. Nevertheless, there are far better ways to customize a fit and get it dialed in close than in days gone by. For instance there are every imaginable size of seat post, neck and crank length to help with bike fit and sizing.