For that attenuation teh speeds are possibly a little low - you would be expecting max attainable figures of 25-28 Mbps UP and 65 to 75 Mbps DOWN (potentially 80 could be achieved).
SNR at 6dB is te normal target.
What is your overall set up? Are the stats taken from the text socket with nothing else plugged in or connected? Do you have any electrical/electronic equipment close to the modem or near to the cables?
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