Explanation: we have an action named "example-teleport". Our action has 2 events. The event we will be using is the teleport event. If we take a look at the Teleport Event page, we can see that it uses 2 arguments.
Argument 1: The radius in which the mob will teleport
Argument 2: The percentage it will execute
So for the above example: whenever example-teleport is fired, our entity will teleport somewhere in a radius of 10 blocks. Since the percentage is set to 100, this action will always happen.
As we have another event "speak", with a percentage set to 100, both lines will always execute which will result in your mob saying : "Try to catch me now!" and a simultaneous teleport of your mob.
The percentage is a mandatory argument. No matter how many arguments you have, your line should always end with a number representing the chance in percentage the event will execute.