Flow Rate Slicing

[Lorenzo infn]

Hi,
I have a question regards flow rate. I have disabled in Advance settings --> override filament setting so it is always 100%.
Then i perform a calibration cube and measured the wall thickness (1 wall only) and i found 0.5 instead of 0.55.
I try to change filament flow rate but when i see the gcode file the E value remains the same.
The same behaviour is present also for infill,bottom/top layer, if i change flowrate the E value remains the same.

Lorenzo