iTunes says I have more storage on my iPhone than I actually do

After syncing my iPhone 5c in the summery it shows that I have 3GB of available storage. When I look at the usage on my actual phone it tells me I only have 1.5 GB of free space. I've cleaned out all of the documents and data that I can, reset my phone, and resynced it but nothing changed. How do I get that 1.5 GB back?

I know it doesn't seem like much but I only have a 16GB phone and need every little bit I can get for work.