CK13N, Std cost for the sub assemblies

Dear all,

I am trying to understand the concept of standard price of each BOM component in CK13N. In some of the Semifinish material ( procurement type - x) shows the activity cost (E) alone as the standard cost of the material. but in some other semifinish materials (procurement type - F) shows the Delivery cost (I) as the standard cost for the material in the FG bom structure.

I need to know, on which basic,the cost element value is piscked and displayed as standard cost for the sub assembly.

Thanks,

Raj V