You can check the memory allocation in your N9 phone by selecting Settings > Device > Data storage (or Memory). Depending on how much total memory you have, the memory is allocated e.g. as follows:
- For installed apps: 4.2GB.
- For app data: 2.1GB.
- For user data: 57.7GB (64GB model) or 9,7GB (16GB model).
With N9 PR1.2 version you can also view a list of the installed applications and the application data consumption.