it depends on what your downloading, how busy their servers are, how fast their servers are. What else is going on your machine, are you downloading more than one thing.
It totally depends on the network and has very little to do with your ISP usually. You can google for "speed test" and you'll get different results everywhere. the link below gives me about 960kbps, but at; http://www.speakeasy.net/speedtest/
I reach 4230kbps.
Also note there is a difference between kilo-BYTES per second and kilo-BITS per second since there's 8 bits in a byte one number is 8 times larger.