The purpose of this feature is to see Warranty Contracts Sales History in the Customer Details and Unit Details screens.

When you go in the Customer details, under the Unit Purchase History tab, the Warranty Contract records along with Unit Sales deals are displayed. Warranty Contract records should have a dedicated icon (Red “W” on blue background). Double-clicking on a Warranty Contract record will open the document:
 

 
In the Unit Details screen -> Purchase History tab, you can also see the Warranty Contract records for the Unit: