Not all the money of the refund was gven back

https://www.peopleperhour.com/stream/view?id=23201268&ref=dashboard-buyer

In this project, the other side never answered, I asked for a refund, it was done, but instead of 50€, it was done 37.5€.

Now I should pay 12,5e more to the new guy, why this please?

Thank you