From test below :
VOL = +63 > +12db
VOL = -32 > -12db
New project
Flex playing at 0db sine wave
Fx 1 and 2 set to none
VOL = +63
No clipping
VOL = +63
Attributes Gain = +0.5db > clipping
VOL=0
Attributes = +12db > clipping
VOL=-32
Attributes = +24db > clipping
Sample gain staging order seems to be :
Attributes Gain > VOL > Fx1 > Fx2 >Track Level > Main Level