I just booked a First Class ticket for my wife LAX - LHR.

AA.COM FAQ states:

Q: What does "Premium Service" mean?
A: Premium Service is offered in the First Class cabin of three class configured aircraft on Trans Continental or International flights. Additional in-flight amenities are provided for customers traveling in this cabin. This service may require the use of additional mileage.

What in-flight ammenities are they referring to? How much additional mileage is required. Are they optional or must they be purchased?