What is GE's gas turbine 'CA_CRT'?

What is GE's gas turbine 'CA_CRT'?

Depending on the change in the CA_CRT value, the DLN Mode also changes, and the TurnDown Valve opens and closes,

but I can't quite understand what CA_CRT is even after looking at the logic.
If I recall correctly, it is the Model Based Control value of combustion reference temperature. In the data I have it is 0 to 100 percent. All the mode switching constants are therefore also based on the 0 to 100 percent scale.
 
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