Canonical Registration ID and message ID format

I have a problem with understanding Canonical Registration Id and getting it returned by Google. I have deliberately registered my Android app twice (to test Canonical Registration Id) but when I try to push a message to both Registration Ids I don't get in the return from Google a Canonical Registration Id.

In addition, I would like to know what the format of the message Id returned by Google means. I can see in the log that it seems to consist of three parts <something>:<something2>%<something3>. Any idea what they mean? Does the 3rd part identify the device?

[INFO com.bipper.filters.PushUpdatesFilter] [ messageId=0:1349819220154718%921c249a6e2555b5 ] [INFO com.bipper.filters.PushUpdatesFilter] [ messageId=0:1349819220242456%921c249a6e2555b5 ]