This is trying to show you that if you know the rules of the code, you can figure out the whole message from only having a part of it.
In this picture, the rules of the code are how the letters are formed.
This is an important concept for communication. It's related to the questions of
. . . Can you understand a person on the phone if there's also static or noise mixed with his voice ?
. . . Can you accurately decode a digital message made of 1's and zeroes, even if some of them are missing, or got reversed on the way to you ?
The answer to both of these questions is 'Yes, you can. If you have ENOUGH of the message, you can fill in the missing parts.'.
In this case, I hate to say it, but I don't think the question gives us enough of the message for us to be able to fill in the missing part. Maybe some people can look at this and understand what it says, but I can't.
To show you a better example of how you can fill in the whole message when part of it is missing, I made my own, and it's attached to this answer.
