Discount Rate % and Internal Rate of Retunrs %

[Geeky]

Got the message as below when cost plan is added.

How Discount Rate % and Internal Rate of Retunrs % and Net Present Value are calculated? And why it did not calculate for below example?

[Your Express]

I think you do it right in this example, which usually works for me. I am not a professional; another person installed my software, but it looks like this. 
I also had some problems calculating discounts, so I called a more professional guy eager to help. He said that I needed to understand the logic behind the program, and then it would be much easier. He showed me all the processes I needed to know, and now I just repeat after him. We often work with discount websites like https://heydiscount.co.uk/, and we need to have all the discounts calculated correctly. It takes some time, but it’s cool after all.