2 sets of contacts displayed in outlook 2013

I have a user that is using outlook 2013, and under his contacts, it displays 2 sets of contacts. He's complaining that sometimes when he adds contacts on his phone, they don't sync with outlook.

I've attached a screen shot of what I'm referring.

How do I delete the other set of contacts folder, because I did a right click, but there's no delete option?
ContactsM.jpg