How to correctly input drag for older missile API?

[DSplayer]

Btw by older missile API, I'm talking about the API used by missiles like the R-27 and AIM-54. The newer API used by missiles like the AMRAAM seem to have a more self explanatory way of inputting drag (still a bit confusing since DCS uses its own naming for some drag values).

 

In the ModelData section, there are the sections for Cx and Cy dependencies along with the characteristic square and model params values but I don't exactly know how these values are made. In the case for the Cx and Cy dependencies, I know that they relate to Cd0 and Cy0 respectively but when I try to compare the in-game values for the R-27 with the "R-27 Missile Family Aerodynamics Development Report", I'm slightly confused by some of the values used for Cd0/Cx (specifically Cx_k2 steepness, Cx_k3 bar Cx0 at supersonic, Cx_k4 steepness of the decline after the wave crisis, and coefficient of dumping of a polar).