In order to understand the following properly, you should be well acquainted with ActionScript, since the file requires some advanced scripting knowledge.
The Idea
The idea is to construct a message, which displays a text followed by the size of our file. When we have constructed the message, we want to take each letter and number and place it inside a matching movie clip. This way, we have a number of movie clips, which we can move around in different ways. This is done instead of having the entire message inside a single movie clip, where we would have to move the entire message in the same way. After this, we want the message to follow the mouse in such a way that each letter and number has a position, which it moves towards.