If you operate long haul with augmented Flight Crew, you may have to log Relief Time (REL) / Supernumerary (SNY).
With CrewLounge PILOTLOG, we log Relief time as the "rest time", the time that you were not at the controls.
Depending on your aviation authorities, relief time may, or may not, be considered as flying experience. PILOTLOG gives you the option. When you select "Deduct Relief from Total Time" on the Settings - Flight Logging page, all flight time logged as Relief Pilot will be subtracted from the Total Time on the Totals page and when you print your logbook and reports. As a result, your total experience shows less hours.
However, you should always log the complete Total Time !
e.g. you perform a 14.5 hours flight from LHR 07:00 to LAX 21:30
You should log Total Time 14.5 hours of which you spent 4 hours in the right-hand seat (log as Co-Pilot), 4 hours in the left-hand seat (log as PIC time) and 6.5 hours sleeping in the bunk (log as Relief time)
Total Time : 14:30
PIC : 4:00
SIC : 4:00
Relief : 6:30
Now, if you have selected "Deduct Relief" on the Settings page, this flight is printed in your logbook with a total time of 8:00 hours instead of 14:30.
Flight Time Limits
The same logic is valid for Flight Time Limitations (e.g. 900 hours annually).
With "Deduct Relief" selected on the Settings page, the Relief time is taken out of your total time. There is no need to setup any additional field, such as "stick time". Instead, log Total Time and Relief Time.
Logbook - SNY
In order to print the code “SNY” in the Holder’s Operating Capacity column of your logbook, typically UK formats, you need to log "SNY" in the Type of Operations for the concerned flight.
Continue reading here : Official State Regulations - Recording of Flight Hours