The 0-3 index, is not mean the variable has 4 values. It means there are 4 different bool values for each variable. One for each engine. So you can have Engine.LeftMagnetoSwitch:0, Engine.LeftMagnetoSwitch:1, Engine.LeftMagnetoSwitch:2, Engine.LeftMagnetoSwitch:3 and each one is on or off. The enum values of off, left, right, both & start are probably combinations of those three variables, for each engine.