Q: Why do I have 25G of documents and data clogging my phone?

Hi UFSwimmer,
 

Thank you for contributing to the Apple Support Communities.
 

I see that you have a lot of space occupied by Documents & Data on your iPhone 6s and you've taken steps to reduce the size. According to Check your storage on your iPhone, iPad, and iPod touch, this category contains Safari Offline Reading List, files created within apps, and app content like contacts, calendars, messages, and emails (and their attachments).
 

You can use the advice in the article above to help pinpoint which app(s) are using the space: 
 

Use your iOS device to check its storage

Tap Settings > General > Storage & iCloud Usage > Manage Storage. 

You'll see a list of your apps, and how much storage each one uses. Tap an app for more detailed information about its usage.

Depending on the app, you might be able to delete some of its content, or delete the app and all of its content. If your device is almost full, or you get a Storage Almost Full alert, remove some less-used content.

If you've already gone through this process and didn't regain any space, you may want to erase your iPhone and set it up as new. If your storage looks normal after setting it up as new, you can restore your content from a backup. For help with this process see How to erase your iOS device and then set it up as a new device or restore it from backups.

All the best.