P3D v4 Flags=6 in engine sounds?

Does anyone know what a flag=6 is in engine sounds. The P3D SDK doesn't list a flag of 6.

From the SDK:
Flags have different functions when associated with different sounds:
For all sounds:
0 = no flag
1 = disable sound

For [combustion] sounds:
2 = damaged
4 = boost (not supported)
8 = jet engine rumble sound

For [prop] sounds
2 = max prop pitch
4 = min prop pitch
8 = min reverse prop pitch

My new MILVIZ DHC-2 Beaver sound file, which is awesome by the way, shows Flags=6 on all propeller sounds.