What are Customer Payment Value (CPV) and Net External Sales (NES) - and the relationship between them?

So, I've recently started my first "real" job as a Marketing Assistant in the marketing department of a renowned company. These first few days have been focused on learning about the ways the company works, some "theoretical" things that haven't been taught at college, etc. I'm getting a pretty good grasp on most of it.

However, one thing that has been explained to me were the Customer Payment Value (CPV) and Net External Sales (NES), as well as their relation. This I understood very little - not what CPV and NES actually are, nor the relation between these two.

Can somebody, please, explain these concepts to me and the relation between them? I've searched online and haven't been able to find anything useful.I will ask my supervisor more about it on Monday, but would like to get to understand it previously.

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TL;DR: I don't understand what Customer Payment Value (CPV) and Net External Sales (NES) are, nor the relationship between the two.