Quick Tip help: How to pan 2nd image while using Image wipe?

Hey all,
Wondering if someone can help me with a quick tip. I was watching this video:
and at 13:26 he pan's the 2nd image in the image wipe on the color tab. I wasn't sure how he was able to do that?
Can anyone help and tell me how to set my file up so I can do that in the future when shot matching?
Thanks!
Spencer
Wondering if someone can help me with a quick tip. I was watching this video:

and at 13:26 he pan's the 2nd image in the image wipe on the color tab. I wasn't sure how he was able to do that?
Can anyone help and tell me how to set my file up so I can do that in the future when shot matching?
Thanks!
Spencer