I noticed while syncing some music from my iPhone, the amount of free storage in iTunes is different from the amount of storage in my iPhone. For example my iPhone has free storage pinged at 6.8 GB while iTunes only reads 6.1 GB. It seems to be affected by audio as the audio shows 28.1 GB but my iPhone shows 26.2 GB. Any reason for the disparity? It only seems to be fixed by resyncing all my audio but it takes a long time to resync 26 GB of music. This is after replacing .mp3 song with the exact .m4a song deleting the .mp3 after words. It's not too big of a deal breaker but later on in iTunes will mentioned cannot add more content.