iPhone remote app

I've just downloaded the remote app to my iPhone 5 with the intention of using it to control iTunes on my MacBook pro.

A 4 digit pin code is generated on the iPhone which I then have to input into the 'Remote' tab which appears on iTunes. When I enter this pin code it instantly tells me the pin code I entered was incorrect. When I re enter the same code, it has a think about it for approximately a minute and the again tells me the pin code is incorrect. I've done this too many times now with the exact same result each time.

What am I doing wrong?