Can anyone explain what may make this change, I am currently migrating to PN and noticed that it has changed in the past few hours. I am wondering if this could be the sign of "action" or is it normal for this to change randomly?
Margin or SNR changes are very common. Mine varies between 7 & 16dB on a regular basis. Many things can cause fluctuations including weather conditions, local electrical interference and the gradual deterioration of copper wiring.
An increase in margin means things are better because the strength of the signal you are getting is improved. A 3dB improvement in SNR actually means the signal streangth has doubled as explained in ADSL: Understanding Line Loss and measurements.