Inventory item had a book value of $100 for 8 items (on hand) giving an AvgCost of $12.50 each (Received not invoiced).
 
FYI: PO was issued for 10 items (total $125.00 at $12.50 each).  10 were Received not Invoiced when invoiced was posted 2 out of 10 were allocated to a WO. Those parts were new with no history that could change the average.
 
For testing purposes The  items were invoiced at $150 (total cost was changed from $125.00 - per PO - to $150.00 when posting invoice in AP-C). After posting took place Book value went up to $125.00 and the Average cost from $12.50 to $15.6250.  I was expecting an average of $15.00 (150.00 invoiced divided on 10 items) why it is showing $15.62?
 
I run other test and average came up as expected. Please explain.
 

More than likely the cost for the 2 allocated units will be lower, but my concern is related to the average calculation.
 
2 items at $12.50 will be $25.00
8 items at $15.00 will be $120.00.  
$145.00 divided by 10 will be $14.50. The average should be $14.5 (from that point of view).  
 
In fact the total was $150.00 for the 10 items becuse the invoice was not posted before the items were allocated to WO.
 
The book value is showing $125.00 for the 8 units on hand therefore the average for the remaining 8 units  is $15.62
 
I am trying to undertand how the system works. I must be missing something because the average calculated is not clear. Please explain in detail... if possible.........Thanks

Thank you for the detail........I appreciate your help