Measure of how much the signal has degraded between the DSLAM and the modem. This is largely a function of the distance from the exchange. The lower the dB the better for this measurement."
The distance from your house to the distriution point calculations the speed of your line. The shorter the distance the better speeds you can get from what the exchnage offers and the longer the distance the lower the speeds you can receive from the exhcnage is offering. If the maximum speeds supported on the exchnage in your area is 10240Kbps and your line Attenuation is reading at or less than 20dB you will definitely get 10240Kbps without any problem. But if it is at or more than 40dB you stand a chance of not getting a stable 10240Kbps. You might get a stable speed of 8Mpbs or less.
"If this value is high, then signal quality is low, and vice versa. Is the customer far away from the exchange? Long copper lines could be the cause of attenuation. A value above 55 dB is of concern (bad)."