That's a combination of the OS, Samsung bloat and carrier bloat. Most of it cannot be deleted without rooting, but it would be pointless anyways it's in the OS partition. You won't gain any extra usable space.
That cant be otherwise people who get a 32gb phone would only have 12gb free out of the box. Also, wouldn't the OS be what called System Memory in my screenshot?
I know that I didnt have close to 11.49 on day 1...its been growing.
I went through all of my apps (including the bloat and crap that I disabled) and it is close to the 5.89GB that it says for apps when I go into the detail of used space.
9.43 GB of System Files. 20MB of miscellaneous files. On AT&T. 50GB of free space.
Posted via My Samsung Galaxy S6 Handheld Device
You have nothing for Used Space? That's where all my pics, vids, music and applications are - 12.64gb for me.