Hi Bas,
I’ve had a deeper look at the way OneSignal and the platforms handle badges. Here is a great resource from OneSignal: https://documentation.onesignal.com/docs/badges
On iOS, you need to explicitly set the badge count as well, it doesn’t automatically reflect the number of notifications.
Meanwhile on Android, we currently don’t support the OneSignal SDK version that allows badges to be set automatically, unfortunately.
Best,
Bence