That is for your FSCM/Fuel system. You also have several modes that are a derivative off the fuel system status, when closed loop fuel is active (Found while logging fuel pressure state) ; Normal, High Flow, Low Flow. Fail or Default will show when FSCM is not active if forcing open loop and your default or failed pressure will be utilized. Atleast that is what i have found on my silverado. Not sure what has to be met in order for it to be closed or open. I do know de-activating closed loop (O2 sensors, etc.) my FSCM/fuel system will no longer adjust pressure and fuel system status never goes into closed loop. Hope that helps a little bit.
1961 C-10 5.3 NV3500
2007 NNBS ECSB 4.8