PLEASE EXPLAIN As 2 valuation of inventories

Cogs= (purchases as per the purchase date + opening inventory  - closing stock) 

Profit or loss = sales - cogs - general overheads

Post a screenshot because I'm confused and my mobile is allowing me to see the whole screen 

Sorry if there is no attach link. But i have modified the recent formula and i hope you can make it out. 

Check out with others if there is a replacement cost issue here while calculating nrv. If not things are very easy.