On my iPhone in the About section in settings it says I only have 1.82GB remaining. However, when I connect the phone to iTunes on my Mac and sync, it says I have 11.63GB free.
No one knows the exact reason. But I can tell you, trust whatever iPhone is saying. Don’t trust iTunes info. Problem solved.
Based on my observation, it could be multiple stores. Ways the capacity is calculated. Or some other reasons.