iPhone 6s - 2.03GB of Document and Data

Hello,

I know that this subject has been discussed a lot. But I need some help.

I have a iPhone 6s 16GB that I keep only the very essencial apps. The awful thing is that when I plug it into iTunes I see that there is 2.2 GB of music, 1.06GB of photos, , 2.48 GB apps (45 apps) and 2.03 GB of document and data as shown below.

Now before you tell me the obvious, Ive gone to Settings>General>Storage & iCloud Usage>Manage Storage.

This is what I got:

As you can see I keep my apps really clean and have already done the following:

- Clear all my iMessages conversation

- Clear Safari historic and web site data

- Clear Browser data on facebook

- Clear all conversation on whatsapp

- Erased the "recently deleted" photos on photos app

Now, how is it possible to have 2.03GB of document and data if my biggest app only has 237 MB (157 MB of the app and 82MB of document and data)?

If I sum all the "document and data" of all apps listed in the storage section, I will get for sure less than 500 MB. So where is those GB missing? They must be somewhere!