First let me say, I am a novice when it comes to this.
My disk space is 688 GB and as of right now it shows I have 18.3 GB available.
Looking at the apps I'm using 299 MB.
Under media and files I have the following :
Pictures 42.3 GB
Videos 0 Bytes
Music 3.62 GB
Documents 65.6 GB
Downloads 32.3 MB
Unless I'm doing something wrong, that adds up to 111.85 GB.
What is the other 576 GB being used for ??