Mass Edit Material Costs

I am trying to update Material Cost of an item using standard 'Mass Edit Material Costs' concurrent program. We are using FIFO costing. While submitting the program, I am passing cost type as 'FIFO', Item Number (same From and To), Basis Type as Item and Change Amount as '3'.
My question is, if we have multiple layers available for this item in the current organization, which layer will be updated by this program? Please help.

Regards,
Satya