Why does internal storage claim to have 4gb/4.5gb full when apps are listed as 1.78gb / cache 30mb?

[Help098]

I have just upgraded to marshmallow on a moto g third generation.

I have a 32gb SD card set as adaptable storage with 20gb+ free.

I have tried app cache cleaner and wiping cache partition.

Any ideas? All suggestions gratefully received.

Thanks

 

[thesims2customs]

Is it because of system files?