Odoo CE 12 : MRP Cost Formula

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Dear Deltatech Team,

I writing in hope for your feedback and help
In regard about : https://apps.odoo.com/apps/modules/12.0/deltatech_mrp_cost/#authors

I have installed the addons, and it works well.
I already understand the whole addons flow.
Thank you in advance for your addons.

The only thing that I really don't have any idea is :
How does the addon calculate the Product Cost? Can you please enlightening me about the formula?
Is it Moving Average Method Calculation?

As I keep doing and exploring with numerous Manufacturing Order, however the number of Product Cost and Inventory Evaluation is different from the generated accounting journal.

Thank you and look forward for your reply.