From: Covington LA via Montreal!
At sea fuel transfers are taken into account for the 150/76(38) numbers, as well. So some ships in that TF might have a "range" of 200+ hexes, others only 40-50... The line is (probably) a best guess at:
Max Range /
Required to go to all waypoints, destination, and return home by routing rules such as Direct, Safest, etc.
(Required to get to destination)
You'll note that when either of the last two numbers are bigger than the first, they all turn red (does not take into account refueling at destination or waypoints).
To further elaborate on the "RED" numbers, not all numbers need go red, if you have enough fuel to reach your assigned destination (the number in (x)...) then it will stay green. If you can reach your destination but can NOT return to your assigned point of origin (read home port) then only the first number goes read (meaning you are on a one way ride if you can't get any more fuel). As indicated by others, it is not an exact science but it is a very useful planning tool. A trick you can use to stop excess refueling of the smaller endurance ships is to assign your destination as your home port as well, thus the second number and the (x) number should be equal.