What is inside this evaluation component?

I'm studing the Underwood pavilion which is mainly about design a module based on tensegrity structure system and use calapagos to solve and find an optimal geometric fitness for the two unknown values of rotation and distance between faces. 

but there is one step I still have no idea how to solve it, which is about a evaluation component (I don't know what kind of equation they put inside)

 the attach file is the current file I'm working on