The fact is that your modem and all modems measure the speed in a different way. 56k DOES NOT mean 56 Kb/sec download rate, it means 56 KiloBit/sec. A byte = 8 Bits, so you have to divide this number by 8 to get the real max KB/sec download rate which will be 7 KB/sec as Hellbreather said.
If you are going to ugrade to a broadband connection, don't expect to see another ratio. If you go buy a 1 Mbps connection, you will have to divide 1024 Kbps by 8 to get again the actual download rate which will be 128 KiloByte/sec.