How the system is picking the fixed values in ck13n

Dear all,

Please suggest me as i am not clear about how the system is picking the fixed values in CK13n, Out of my 20 components i have defined material cost as variable and activity as fixed and variable,Overheads fixed and variable.

1. Over heads are bifurcated into fixed and variable but base for OH's are material cost which is varaible.

Please suggest me how i am getting the fixed cost in CK13n

Thanks

kishore