iPhone 6s plus Storage

I have deleted all of my pictures, music, apps, and text messages, and it says I'm taking up 10gb of storage. If you add up all of the little apps that come on the phone under the "storage and iCloud usage" mange tab thing, it's less than a gig. What is taking up so much memory and why can't I delete it? My pictures were completely deleted, i made sure to delete them out of the Recently Deleted folder. I connected my phone to iTunes on the computer, and then synced it. It says on the computer that i have 7gb free, but on my phone it says i only have 2gb free. I restarted it after that just in case that was the problem, and that cleared up .04gb. Im not sure what to do at this point.