What does "My values ​​for 100% of my items" show?

I've read that this is the total purchase price of all my coins. But something is wrong here. The total purchase price of my collection was recently PLN 249,587. In the meantime, I added one silver coin purchased for PLN 141. Now it shows me a total value of PLN 255,629. So as you can see the difference is PLN 6,042 and not PLN 141. So what's going on here?

Prices are adjusted for changes in exchange rate with the Euro.

That's the short version. Here is the long version:

https://en.numista.com/forum/topic104145.html

Thank you for the information but it seems to be a little bit unuseful feature for me. It shows so different amount I paid for my whole collection that it tells me nothing about how much I spend for it in real…

If you export your collection and get the sum of your buying prices does it correlate more with the current larger value or something different?

May be the exchange rate.

Try deleting that coin and see how your My values change. Or better yet, just change the buying value to 0 and see what happens.