You're getting 56/67 on your 50/50 because FiOS TV services share bandwidth with your Internet. For whatever reason, FiOS can't break these services over separate VLANs or can't keep bandwidth separate between VLANS, whatever they're doing. You can even find people, as of 2015, having issues when hammering their Internet, their DVR or TV functions start having pixelation issues. My ISP gives me 50/50, and I get exactly 50/50, well, something like 49.8 in practice. IPTV comes over a separate VLAN, which has separate bandwidth allocations.
Yay, Verizon. I still read about issues with Verizon peering and random problems with AWS, Akamai, Netflix, YouTube, and others. You might have gotten lucky, but many around the nation have issues trying to get 1Mb/s from their 50Mb connection. At least the speed test is good.