Q: iTunes shows different storage information than iPad

When I sync my iPad, it says that I have 3 gigs of free space and 1.2 gigs of books. However, in the storage information on my iPad, it says I only have 1.6 gigs free on the iPad and 2.3 gigs of books. I am curious as to why this discrepancy is happening, and how I can get correct information on how much of my storage I am actually using.