I can't delete music!

I am having an issue with my iphone 5s syncing with my itunes. When I connect my iphone and load itunes, the current version of both, IOS 8.4.1, I click music under "Settings" on the left hand side and I select "selected playlists, artists, albums.." button and even though I have nothing selected under "playlist" or "artist" it says that I have 600 songs already on my iphone. On the left hand side again under "on my device" I click music, when I see that there is music on my phone that I do not want and I cannot delete.

I have already tried deleting all of my music from my iphone under the manage your storage tab and when I plugged my phone back in all of the 600 songs were synced back on to my phone. I just want to be able to sync music that I have on my selected playlist, not all of these other songs that it is trying to sync. Does anyone know how to delete these 600 other songs? Why is this so hard?

Thank you in advanced.