The pie chart shows you how much your company pays to and receives from foreign countries. The percentage describes the volume of your cross-border payments in the given currency.
The volume describes how you payed and received in the given currency. As an example, if your incoming cross-border payments amounted to 1,000,000 EUR and your outgoing payments amounted to -2,000,000 EUR, then your volume would be 3,000,000 EUR. All numbers are converted to your baseline currency to allow for comparison.