Since your wireless test is only measuring 49.8 Mbps, I think widermouthopen is exploring any wireless settings impeding your performance. After you click Edit, what options are available to you...Channel, Channel Width, Quality of Service (QoS), etc.? However, if you want to verify your data plan (Ultimate 500), your wireless speed shouldn't be a concern right now.
You basically have 2 different networks. You have the Cox network...which you have no control...and you have your personal, private home network...which is your router. Your question is about your Ultimate 500 plan so as of now, you only want to test the Cox network.
When you test the Cox network, you want a direct, isolated, unshared connection to your termination point of the Cox network. This termination point would be the WAN port of your modem.
Since you're testing the Ultimate 500 plan (500 Mbps), your equipment will need at least gigabit speed: gigabit Ethernet NIC, at least a Cat-5e cable or if your testing device doesn't have an Ethernet port, at least a USB 3.0 port/adapter.
You don't want to involve your personal, private home network to test your data plan. When you test through your router, your testing device is sharing the network with all other devices connected to your router. Meaning, you're trying to test your total available bandwidth using only a portion of the bandwidth allotted to your testing device.
First, verify your speed test on the Cox network, then we'll explore your wireless.