Slow Internet - despite Docsis 3.0 (Motorola SURFboard SBG6580) + Cox Premier & only 1 computer using internet

Hi -

I just had Cox premier internet installed, but it's very slow.  Premier is supposed to get you upwards of 100 Mbps download speeds, and 10 Mpbs upload speeds.  I ran a Cox speed test and it says I'm only getting 31.54 Mbps download and 2.77 upload speeds.  Also, my dioceses 3.0 modem/wireless router is brand new and I think is one of the better ones out there (Motorola SURFboard SBG6580), plus I only have one laptop connected at the moment.  I also don't think this is a peak time to be using internet, so aside from the more typical reasons for slow connectivity, can someone troubleshoot why I'm not getting much higher speeds?  Thanks for any help.