EXFO FTB-500 (Window XP) - Manual (Page 131)

Using the Optional Built-In Power Meter and VFL
FTB-500 121
Clearing Measurements from the Display
Clearing Measurements from the Display
When measurements do not meet your requirements, you can clear the
display and start over.
Note: Clearing measurements from the display does not delete them from the
disk (if they were saved previously).
To clear power measurements:
1. From the button bar, tap Close.
OR
From the Measurements tab, tap Clear All.
If you have not saved the measurements already, the application will
prompt you to save your work.
2. Select Yes to save the file.