ok i don't have D3 (0.1) in Signal ATT ?

That indicates that the D3 band isn't being utilised. Typically because there is high attenuation for the tones in D3, and the signal-noise ratio for the tones in that band fall primarily below the SNR margin.

So that possibly also answers your other question of why line attenuation and signal attenuation are different. Line attenuation shows the aggregate attenuation across the tones allocated during the medley stage for that band, while signal attenuation is an aggregate calculation based only on utilised tones in a band.

As

*c6em* notes in the link provided by

*kitz*, there is a mathematical equation for calculating aggregate attenuation which is given by..

It initially looks daunting, but it's not.. NSC=number of Sub-Carriers, and delta f is the subcarrier spacing (4312.5Hz)

cheers, a