Are you sure you're getting your "B"s and "b"s correct?
ISPs advertise in bits while downloads are usually in Bytes. 1 Byte is 8 bits.
So a 1.5mbps line is 1,500,000 bits.
1,500,000 bits / 8 Bytes/bit = 187500 B or 187.5 KBps in speed. So 200 kBps is right as many ISPs will go over a little bit.
Also remember that the server you are downloading from will also determine your speed. It may be running at a slower speed than you are.