EXFO FastReporter 2 - Manual (Page 166)

Working with OTDR Files
156 FastReporter 2
Setting Span Positions with Absolute Lengths
4. Select whether you want to enter the span length or the receive fiber
length, then enter the appropriate value. The other value is updated
automatically according to the value you have entered. If no event is
present at the new position of the span end then, it automatically
creates a new event.
5. Click OK to save the change or Cancel to discard it.
Note: When a new event is created, the exact event position, event type, and
measured values are automatically determined to have the best
characterization for the most probable event present in the area. When a
new event is successfully created, the event is marked with an asterisk (*).
Note: If the origin of the selected file origin does not allow modification, an error
message is displayed.