Iphone storage is not adding up?

When I go to Settings>Usage it only adds up to around 3 GB but the phone says I have used 11 GB. I tried setting my phones time back to see if there would be phantom photos in the recently deleted album but there were not. I don't know what else to do and I'm getting really frustrated any ideas?

Clean your phone using cleaning apps, you may have unwanted files aka thumbnails

You're confusing Ram with Rom. The iPhone 7 has 3GB or ram in which applications and the OS are executed on. The Rom is what holds your video's pictures and music etc…

Also the OS itself uses some ROM. A 16GB iPhone for example will only typically have about 11GB of free storage that's available to you to use.