System Memory issue

Currently using my 16GB Iphone 6 as a music player ONLY using ITunes . My OS is up to date and running 12.3.1.

My understanding is that this Software version requires anywhere from 1.5 to 2 GB. I have reset my iphone and have deleted ALL of the apps that it would allow me to delete.

I currently have 8.26 GB of memory dedicated to Audio files. 10.2 MB is dedicated to the apps I could not delete. Under the "System" designation it is indicating that 6.74 GB of memory spaced is being used. Leaving 1GB "Free" Total GB = 16 GB give or take. It appears that there is around 4+ GB of unknown garbage chewing up 25% of my storage.

Now when I connect my Iphone to Itunes it is telling me I have 7.67 GB of "Audio Files", 1.27GB of "Documents and Data" and 1.29 GB of "Other" with 1 GB "Free, (946mb) Total GB = 11.23GB give or take. Where is the remaining 4.77GB.

Why is there this discrepancy? Logic would dictate that this is where my issue may be.

Any ideas as to what is going on?