BOAC is right, you are a little confused! Your part A will specify a single engine range for PLANNING purposes, it will also say zero wind conditions, once again for planning purposes. My manual says for the 73cl 360 miles and for the 73ng 370 miles. What you do enroute, during actual flight, may be completely different!
To many scenarios to discuss briefly here!
Listen to the old dinosaur though, usually he's right :-)