It is exactly as you think, but you only went down 1 layer. 8 bits = 1 byte, 1024 bytes = kilobyte, 1024 kilobytes = 1 megabyte, 1024 megabytes = 1 gigabytes.
HOWEVER most manufactures use 10bits = 1 byte, 1000 bytes = kilobyte, 1000 kilobytes = 1 megabyte, 1000 megabytes = 1 gigabyte etc. So manufactures actually print that DVD's are 4.7GB, however in reality they are only 4.36/4.37GB in size.
It is a marketing gimmick to make it look like DVD's and other storage media can store much more, but it is basically lying directly to the unsuspecting consumer.
With DVD's there isn't much loss (333MB), but when you start getting into the 1TB and 2TB HDD then you can loose ALLOT of space from what your actually paying for (up to 100GB for 2TB drives).
It is something that really should be banned in the technology sector.