Messy stats let me see if I have this right
Downstream attenuation of 2dB, margin 7dB
Upstream attenuation 0dB, margin 6dB
Connected at 21Meg down,. and 679Kbps upstream.
The Power levels (PSD) suggest modem has backed down from the maximum power, which is no surprise at that distance from the exchange, which is must be next door.
The 6dB will be the target, and so seeing that is not really a worry. More importantly is does it vary over time, so time to check the router logs to see if there is any history, if not try router stats lite to monitor the router. Failing that login in perhaps once an hour particularly when dark and keep a note of all the figures.
What concerns me is that the upstream is lower than I would expect, so it is worth checking your wiring in the home, and that everything is filtered, and also seeing if using the master sockets test socket helps with the stats.