[Koha] Circulation Rules: Parent and Child Item Type

Dear All, In our library we rent textbooks for a semester at 10% cost of the book. To manage this in KOHA, I created a Parent Item with around 60 child items. Each child item has a different rental charge. I have applied a lending policy on the Parent Item with the understanding that it will apply to all child items. However I am not getting the desired result. To get my desired policy, I have to apply the lending policy to each child item. I don't think this is correct behavior but I don't understand what I am doing wrong. With best regards, Naveen Ali ITM-JE (EAKL) Inst Representative for HEC Digital Library Resources. NEDUET, Karachi.