What this means in practice
Because each plan already carries its own default store, requesting another managed store is not the way to increase capacity; add space or connect an external bucket instead.
Practical guidance
The account receives its default object storage automatically, so there is no setup step to create the first bucket before saving objects. Each plan has one default storage allocation; requesting another default instance is rejected because the existing one already serves that role. This avoids splitting platform-managed files across multiple default destinations.
Use the provided storage as the destination for supported account features and check its current usage when planning what to keep. If you need a different bucket, connect an external R2 or S3 bucket rather than trying to create a second platform default. The distinction matters: the managed default is provisioned with the account, while an external bucket is a separate resource that you configure and connect. Check the account's storage view to understand what is already using the included space.