Geometry measurement, from where to where I'm looking at http://www.specialized.com/ca/en/bikes/road/tarmac/tarmac-comp#geometry and would like to know what "Seat-Tube Angle" means. For say the 56, I would assume that angle is like this 



Where the horizontal black in parallel to the earth, the red is the bike frame and the blue is the angle.

Am I correct in my assumption?

Thanks!
Yes, you are correct. The seat tube angle is measured relative to horizontal. 

There is also a separate angle called "derailleur angle", which is measured between the seat tube and chainstays. You'll rarely find it specified in the geometry data though...