Wrong fixed price

I’m using the plugin on my website.
The discount activates as you have more than 50€ in the cart.

My problem is on fixed discount.
Now I’ve set 5€ discount. The message in the topbar is right, while in the cart it says 5.50€
If I set 10€ fixed discount it set 11€ and so on.

With percentage discount it works correctly.
I’m not using any custom or autochange price function.

Can you give me advice on this?

Thank you