Luftfahrer From Germany, joined Mar 2009, 988 posts, RR: 2 Reply 1, posted (3 months 22 hours ago) and read 1833 times:
You can put in the amount of fuel (in kg or lb) you plan to have as a reserve at your destination airport. If the FMC computes that you would have less fuel in the tanks than the value you have entered, you would get a warning saying either 'INSUFFICIENT FUEL' while on the ground or 'USING RSV FUEL' when you are already in the air.
'He resembled a pilot, which to a seaman is trustworthiness personified.' Joseph Conrad