BOM Costing for Bottling production

I am trying to setup ERPnext BOM to tea drink bottling process. The process is mixing, cooking and filling, left over tea can be used on the next batch.

  • 1 bottle is 1,000ml
  • One cook batch size is 100,000 ml
  • During cooking, assumed around 10% evaporates, which leave us with 90,000 ml going to filling process
  • During filling, some can spill out, and only 87 bottles filled and 1,100 ml left

This is my B.O.M for 1 batch (90 bottles)

  • Tea leaf: 1 Kg
  • Water: 100,000 ml
  • Sugar: 1 Kg
  • Tea : 1 ml (updated in manufacture transfer stock entry)
  • Bottle: 90
  • Scrap item: Tea

I am having issue on calculating rate/cost of scarp item, it use existing rate rather than cost of incoming material.

Pls help…