I get this prompt sometimes when I connect my phone to my computer. It doesn't tell me what items it's referring to, but I know I don't want anything on my computer that isn't there already. But it looks like if I don't go ahead with it, the mystery items will be removed from my phone.

Anybody know what the thinking is behind this? Maybe it's just a sync setting I've set myself, but it reads like some kind of crazy ransom note :)

I chose 'Don't Transfer' in the end. I have no idea what the consequences are. I don't notice any differences on my phone.