"Pairing" means the AppleTV will only recognize a particular remote, so you can use separate remotes to control different Apple devices in the same room. I "learned" the same codes as Michael but with a different last 2 digits, so my guess is those last 2 digits identify the remote for "pairing".

The short codes work for me on a TSU3000, but not completely reliably. I was able to improve this by adjusting the duration. 0.25 seconds works reasonably OK for me. The AppleTV is still sometimes finicky about how you aim the remote, though.

The long codes did not work for me except for the play/pause code that Mitch posted.

I hope this helps.

Carl