Each link can have how many redirections as you want, you may want to have one of those redirections used more ofter than another.
To do so use the weight configuration of each redirection.
Let say we have a link lyndra.net/example with one redirection to amazon.com with a weight of 3 and one redirection to google.com with a weight of 1.
Then around 3 out of 4 times lyndra.net/example will redirect to amazon.com and 1 out of 4 times it will redirect to google.com.
Note that each redirection can have a weight between 1 and 10.