GarageBand Stereo.

I own a POD HD500X by Line 6. I normally use headphones directly from the pedal to listen, but I wanted to use it for recording through GarageBand. I have a stereo delay set up on the pedal board and it is very noticeable when using headphones. But, when I plug up the USB to my Mac and try to play I get mono instead of stereo. I've tried using other recording applications to see if I'd get stereo, and I did. So it must be somewhere in GarageBand that is not right. Anyone have any ideas as to why this will not work?