CryteEngine3 has multiple files defined for multiple purposes. Example:
ObjectDetails, Shading, VolumetricEffects etc...
And each of this config file definition has multiple definition for each type of settings:
Low = 1, High = 2, VeryHigh = 3, Extreme = 4 etc... ( obviously you will not see "Low" in the options Crytek purposefully made this option unavailable )
However when I looked at the config files, most of these definition were defaulted to "3" which is very high. Which means even if you set the graphics options to "4" some configuration like "ObjectDetails" is defaulted to "3" and no configuration for "4".
I also found one more thing that is pretty silly:
sys_spec_Quality.cfg has difinition for both Low[1],High[2],VeryHigh[3] and Extreme[4].
The only questionable part of about this file is that the definition for both Low, and High isset to value of "1". And the difinition for VeryHigh are all set to a value of "2"". and wait there's more, Extreme config definition is set to "3".
So to some it all up:
if CryEngine encounters a command "sys_spec_Full = 2" then "Make all config to low"
if CryEngine encounters a command "sys_spec_Full = 3" then "Make some config high and some low"
if CryEngine encounters a command "sys_spec_Full = 4" then "Make all config high and if no definition is avaiable set the value to default which is equals to sys_spec_Full = 3"
So there you go "Extreme" settings is nothing more than telling the engine to default everything to "VeryHigh" if no definition is found which if you just just take a peek to the config files, all were defaults to "[3]VeryHigh".