That is the correct setting for the 777-200 Cleared for takeoff (KSEA) saved flight file because the engines are already started. The 777 does not come with a cold and dark flight, so you have to create your own. And here are the settings after turning the fuel control switches off:

[Engine Parameters.1.0]
ThrottleLeverPct=0.00579833984375
PropellerLeverPct=0.9996337890625
MixtureLeverPct=0.9996337890625
Pct Engine RPM=0.36098571739045981
MaxReachedEngineRPM=20389.098947171507
LeftMagneto=True
RightMagneto=True
GeneratorSwitch=True
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=0

[Engine Parameters.2.0]
ThrottleLeverPct=0.00579833984375
PropellerLeverPct=0.9996337890625
MixtureLeverPct=0.9996337890625
Pct Engine RPM=0.41046477772108736
MaxReachedEngineRPM=20389.098947171507
LeftMagneto=False
RightMagneto=False
GeneratorSwitch=True
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=0

Now. Let's take a look at the Captain Sim 767 file, 767-300 Cleared for takeoff (KSEA), settings. The MixtureLeverPct settings are pretty much the same as for the:

[Engine Parameters.1.0]
ThrottleLeverPct=0.005828857421875
PropellerLeverPct=0.99969482421875
MixtureLeverPct=0.99969482421875
Pct Engine RPM=0.65387755443201345
MaxReachedEngineRPM=7546.9248302787046
LeftMagneto=True
RightMagneto=True
GeneratorSwitch=True
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=0

[Engine Parameters.2.0]
ThrottleLeverPct=0.005828857421875
PropellerLeverPct=0.99969482421875
MixtureLeverPct=0.99969482421875
Pct Engine RPM=0.65387755443201345
MaxReachedEngineRPM=7546.9248302787046
LeftMagneto=False
RightMagneto=False
GeneratorSwitch=True
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=0

And now the 767-300 Cold-n-dark (KSEA) file engine settings:

[Engine Parameters.1.0]
ThrottleLeverPct=0.00567626953125
PropellerLeverPct=0.999267578125
MixtureLeverPct=0
Pct Engine RPM=0
MaxReachedEngineRPM=0
LeftMagneto=True
RightMagneto=True
GeneratorSwitch=False
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=False

[Engine Parameters.2.0]
ThrottleLeverPct=0.00567626953125
PropellerLeverPct=0.999267578125
MixtureLeverPct=0
Pct Engine RPM=0
MaxReachedEngineRPM=0
LeftMagneto=False
RightMagneto=False
GeneratorSwitch=False
CowlFlapPct=0
FuelPumpSwitch=False
CarbHeat/DeiceSwitch=False
Afterburner=False

From that cold and dark setting for the 767-300 (the CS 707,727, 737 and 757 all have the MictureLeverPct=0 in their Cold-n-dark (KSEA).FLT FILE), I can start the engines by simply turning the Fuel Control Switches to the RUN position.

When I saved the 777 flight (where I only turned the Fuel Control Switches to OFF (fuel cutoff), then looked at the MixtureLeverPct= setting, I also went and changed them to MixtureLeverPct=0. When I restarted FSX, using that file for that test, to bypass the start screen, I could not stat the 777 unless I pressed CTRL+SIFT+F4!

So why is it that when I set the MixtureLeverPct setting set to MixtureLeverPct=0 for the 777, that the engines will not start unless I press CTRL+SHIFT+F4? It is this difference, that make the 777 not start from the default C172 in a cold and dark setting. ALL my other addon jet airliners start by turning the Fuel Control Switches to RUN, only the Captain Sim 777 doesn't start.

Here is why I think it is happening. I believe that the animation tag for the Fuel Control Switches is different to those used in the other CS aircraft, which stops the 777 from starting the engines when the setting in the saved FLT file is MixtureLeverPct=0. :(