just a book a trip to milan and out of rome for march.
in my itineraries it says on the way back FCO->IAD 0 award miles. can anyone explain?

Booking class: V
Economy
0 Award miles
Lunch, Snack
Flight: Confirmed
17J
Download to calendar
Flight details
--% On-time
4505 miles traveled
[Lunch, Snack]
Economy
0 Award miles