RSVPify and Stripe fees are taken out of payment immediately when the payment is processed. If you chose to enable fee pass through to your customers, you will be able to see the fees in the RSVPify exports.
If you are not passing fees to customers, you will be able to see the total service fee amount in your Stripe account. Log in to Stripe and then navigate to Reports > Financial Reports. The total fee amount is included in the 'Charges' section.