The easiest way for me to understand it is to think of it as holding 2 separate tickets.
Ticket #1 is good for 5 days in the 4 main parks, 1 park per day. You have 14 days to get your 5 visits in.
Ticket #2 is good for 5 WPF&M "visits". You can use more than 1 per day, but if you do, you will have fewer visits left on your ticket at the end of the day.
Example:
Day 1: Magic Kingdom (uses 1 of 5 main park "days")
Day 2: Animal Kingdom, Blizzard Beach, Typhoon Lagoon (uses the 2nd of 5 main park "days" and 2 of the 5 WPF&M "visits")
Day 3: Disney Quest & rest at the pool (uses the 3rd of 5 WPF&M "visits").
Were you to do the above, you would have 3 main park "days" and 2 WPF&M "visits" left on your ticket and 11 days left to use them up. But, if you only visit 1 main park OR use 1 WPF&M option PER DAY, your "5-day WPF&M" ticket can indeed be stretched to 10 days of fun.