Why don't I have any internal space on my S5?

[AC Question]

No internal space on S5

I have not downloaded anything and it says;
Internal Storage
Total Space 16.00GB
Available -6158314496.00B
Apps ( app data )
20.98GB
Cashed data 771MB
Phone Storage
Total Space 16.53GB
Available 13.88GB

Yet I keep getting a warning message saying my phone has no more room. Any help please.