As you received the response from Support Atlassian System, I'd like to share this with our community in order to explain who else may could has the same doubt.
The Starter License supports 5 repositories and 10 committers per repository. All other licenses support unlimited repositories and unlimited committers per repository.
However application will hold as many repositories as your hardware configuration can handle without become unavailable because of lack of resources. We don't have specific information about that but you may want to take a look inside "Hardware requirements" session of documentation in order to get more information.
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