In many situations with gig speed accounts I have seen in the past, I will use speedtest.net's downloadable exe file found on their website. They actually reccomend using the app for speeds higher than 100mbps because of limitations with web browser based speedtest. You should try that and let me know.
Further more, do you know if your computer/device can handle 600mbps or higher, let me know? Im always willing to lend a helping hand to my fellow internet users.
Your signal looks to be withing range for comcast to operate correctly, snr looks good as so do your upstream and downstream levels.
Your upload speed appears to be correct to speed plan, however your upstream levels should be around 40-47dbmv im my experince, gives more resilience when dealing with heavy spikes of fm ingress.
Let me know!
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