EXFO FTB -5240S/5240BP Optical Spectrum Analyzer for FTB 500 (NS-1434) - Manual (Page 363)

Managing Results
Optical Spectrum Analyzer 355
Managing Spectral Transmittance Test Results
You can also move the markers directly on the ST Graph tab. Drag the
marker to the desired area in the display. You will notice that the
corresponding box in the Markers tab changes according to the
marker’s position. If you want to set a precise value for the marker,
simply enter it in the box.
Note: After using the zoom tools in the ST Graph tab, you can only move the
markers again on the graph after deactivating the zoom. Pressing the
arrow in the zoom tools section will deactivate the zoom function.
Note: Markers A and B cannot cross. Displacing a marker over the second one
will cause both markers to move together.