Rickford...I too have found discrepancies with the Cox speedtest to the Cox servers. I'm here in OC, and subscribe to the Premier which is rated at 200Mbps and 10Mbps. Using the Cox speedtest to my local OC area and to distances far away gives interesting results. Over 2wks ago, my Uploads were almost 2x faster than I'm now getting. Here are some numbers I just got.
Wichita= 60Mbps Down, 5.6Mbps Up........Oklahoma= 64/3.0....New England= 26/11....Nova= 26/11....SanDiego=214/6.2 ...OC=232/5.7
Conclusion, for me, OC and Sandiego has the highest download because of the proximity to me, but very low Upload (again, this occurred couple of wks ago) . Going across the country, I should get the lowest downloads, which I do, however, I get the best Uploads....go figure. My numbers to Okl and Whchita sit about mid-range speeds, as expected.
Your subscription of 30/3 may make it hard to get large range of test results, but, you can still see large % variations. I think these speedtest tool, and there are many that I've used....all are useful, but give different results. Times of the day and probably many other factors tend to taint the numbers. I have used others, speedtest.net, ATT etc and get 11+ to my OC or local area but the Cox test gives lower, except when going to New England...weird.