HT4623 Why my iphone low on storage

So I have nothing on my iphone 4. I have no pictures, no videos, no music, no apps, no movies and Icloud is turned off. I have reset my phone many time and the storage is still saying 6.3GB used and 40.1MB available. I am trying to get the new update but I need 983MB to get it. If someone will help I will be very greatful. I have nothing on my phone and still confused to why it won't let do the software update.