What's the difference?
Fiber Route Miles: Fiber Route Miles are measured by the conduit length. A conduit can have 12 – 1024 fiber strands inside it. If you own 2 strands of fiber inside a conduit, you own zero fiber route miles. The owner of the conduit owns the route miles.
Fiber miles: Fiber Miles are measured by taking the number of strands in a fiber conduit and multiplying that number by the route distance of the conduit. For example, a 10 miles of conduit with 144 fiber strands = 1,440 fiber miles.