The 4 day ticket is the number of admission days at a park. The 14 day expire is how many days after the first use that the ticket expires. If you don't get the park hopping option you'll have to go to only one park per each day you use it. If you add the park hopper option, you can go to all 4 parks in the same day if you wish.
You could go to a park the first four days and wait until the 14th day from the first use to go to the water park and it would be ok.
Make sense?