Couldn't update cost with R41815

Hi All,

I want to change item cost level from 2 to 1.

Item Costs;

(Branch/Plant names are examples, not real)

Cost Method	Branch/Plant 1	Branch/Plant 2	Branch/Plant 3	Branch/Plant 4
02	,3000	,3000	,3000	,3000

Costing Methods;

Sales/Inventory = 02

Purchasing = 02

I've run R41815 in proof mode with these processing options ;

Level Inventory Costs = 1

Branch/Plant = Branch/Plant 1

Update Mode = Blank

Print Mode = Blank

The result is like that

I couldnt change item cost level. How can ı do this?

Thank you.