I got clarification and you do not get any benefit from buying the contract later. You may benefit from buying now because of inflation and the help of the GB negotiating a lower price.
In regards to the number of years and how it works his is the exact example used....
If 2 people buy a car on the same date 9/1/11 and one of them buys a 6 year plan on the day he picked it up the car. His warranty expires 9/1/17
If the second person buys the warranty on 9/1/15 his warranty expires on 9/1/17…. The same day as customer # 1
Hope that clears that for anyone who was confused