About space

6 GB is a fairly typical installation. I am seeing 5.9 GB here, as well.

16 GB is enough for iOS, and for a little local storage.

A 16 GB iPhone model is capable of making calls and such, for streaming content when we’re in areas where the network connection is fast and robust, but 16 GB is not a good choice for folks that want to listen to or want to watch much media, or that need to store files or presentations locally.

But to borrow the likely-a-typo from the previous response, 16 GB is an “underspend” for many of us.

The purchase price difference between 16 GB and larger-capacity iPhone models can be (often is) a trade-off between having to continuously manage our storage contents, and being able to load copious media and only managing our storage occasionally.

Uploading stuff to iCloud or elsewhere is the option, if not replacing this iPhone with a higher-capacity model.

Some additional reading:

Set up and use iCloud Photos - Apple Support

Delete music, movies, and TV shows from your device - Apple Support

Hello tgang2xx,

We underspend that you want to know why System takes 6GBs. We're happy to provide you information about the System category.

"Content categories 

The used content on your device is divided in these categories:

• Apps: Installed apps and their content, and content stored in "On My iPhone/iPad/iPod touch" directory in the Files app, and Safari downloads 
• Photos: Photos and videos stored in the Photos app
• Media: Music, videos, podcasts, ringtones, artwork, and Voice Memos
• Mail: Emails and their attachments
• Apple Books: Books and PDFs in the Books app
• Messages: Messages and their attachments
• iCloud Drive: iCloud Drive content that has been downloaded locally to your device. This content can't be automatically deleted.
• Other: Non-removable mobile assets, like Siri voices, fonts, dictionaries, non-removable logs and caches, Spotlight index, and system data, such as Keychain and CloudKit Database. Cached files can't be deleted by the system.
• System: Space taken by the operating system. This can vary based on your device and model."

For more information about the storage on your iPhone check out this article: How to check the storage on your iPhone, iPad, and iPod touch

Let us know if you have any questions.

Thanks for using Apple Support Communities.

Have a great day!