Originally Posted by Kamilkar

Keep in mind that the 20Gbps is shared with other users on your server, that may be a first explanation.
Now if you are experiencing very low download speeds that may be something else. What DS speed are you getting and how much is your connection ?

I get upto 4Mbps on other downloads/uploads total on my connection, but Filezilla gives me 1.5Mbps over all files downloading. The consistency of speed at 1.5Mbps hints at some kind of limit rather than bandwidth share, in which case it would fluctuate somewhat.