Formula of cost amount adjustment AX 2012 R3

I have a question about the weighted average costing method. How about AX calculate the weighted average for an item? How is the closing inventory for weighted average cost item? In my case, P.O received but not invoiced and our formula for cost price = Physical amount/ Physical Qty. I can’t understand the formula of cost amount adjustment when I run re-calculation.
Help me!
Please.