We have subscription software for Windows where the number of paying authorized user for a customer account are managed via a web interface. We were thinking a

We have subscription software for Windows where the number of paying authorized user for a customer account are managed via a web interface. We were thinking about writing an iOS app to let the customer manage her users from an iPhone. Currently users extend their subscription by buying more subscription time via an interface. Could I add an InApp purchase via Stripe at about 2,90% + 30c or because the Windows software is digital (although not consumed by users on iOS, only the user administrator might use iOS) I should then pay Apple a 30%?