There's no data limit, up to 200Mbps is available in my area so 100Mbps shouldn't be a problem, plus they have a policy of not slowing download speeds even during busy hours. I mean I'm getting like 30-50Mbps on my mobile and a wired connection but I'd expect that only on wireless, I'm getting 10Mbps on wireless but I'm pretty sure that's my wireless cards fault because it's old.
I'm thinking they've set something up wrong on their end because the 50Mbps is the package below the one I have and they've just set something up wrong. The dual band wifi has 5Ghz and 2.4Ghz and the 5Ghz does 50Mbps and the 2.4Ghz does 11Mbps according to their router monitor.
Although interestingly my computer does say the wired connection can do 100Mbps but won't go anywhere near that fast.