Workflow: 

1. Create a new product named PHT, which falls under the category of storable products, with an average cost and an automated valuation. 

2. Purchase and receive 1 unit of product PHT for $10 (WH/IN/00012). 
The cost of the product is $10, resulting in a total value of $10 when divided by the quantity of 1. 

3. Purchase and receive another 1 unit of product PHT for $10 (WH/IN/00013). The cost of the product remains $10, resulting in a total value of $20 when divided by the quantity of 2. 

4. Purchase and receive another 1 unit of product PHT for $20 (WH/IN/00014). The product cost is $13.33 due to the average costing method. The total value is $40 when divided by the quantity of 3. 

5. Sell and deliver 1 unit for $13.33 (WH/OUT/00033).

6. Then we sell and deliver the rest of the quantity 2. (WH/OUT/00034)

If the product unit cost is $13.33, the journal entry should display $26.66.

Nevertheless, Odoo indicates $26.67 due to the average cost differing from the total cost. 

The total cost from steps 2 to 4 is $40 (10+10+20) (Quantity 3). 

But as a result of average costing, Odoo automatically adjusts the unit cost to $13.33 = ((10+10+20)/(1+1+1) (total value/total quantity).

If all three quantities are delivered, the total cost is $39.99 (13.33 * 3), not $40 (the original purchase value). There is a $0.01 variance.

Upon delivering the remaining quantity of 2, instead of $26.66 ($13.33 * 2), Odoo included an additional $0.01 for the adjustment in average cost, resulting in $26.67.