Number of audio files on iphone different than in itunes?

In the itunes iphone music sync page it shows 587 files, but the itunes library has 588 audio files. How do I find which file is not syncing?

It's possible there's a file the computer can't locate. Scroll down through your songs, and look to the left. If one has a grey symbol, I believe it's a checkmark or an x, it can't locate the file. Right click, then click 'more info' and it will ask you to locate it.