Stopped sync of photo's with iTunes, iPhone still claims little storage is used due to sync
While I am unsure of the EXACT details of what may be left in that 0.7KB I  know your phone saves information about what computer it connects to so it knows it can trust it for syncing files, updating software, backing up, and so on. Along with information about what you do and do not want to be synced on the phone. All of that information is still needed whether you sync everything or nothing but would take up a very tiny amount of space, as you can see.