That's only if you decide to install absolutely everything that Debian supports -- which includes not only the base system but several desktop environments, several dozen window managers, at least three entire office suites that I'm aware of, four different HTTP servers that I can name off the top of my head, several dozen programming languages and full library suites for each, several different development environments, at least a half dozen full SQL database servers, whole hosts of scientific/electronic/mathematical application suites, and so on and so on...
Debian is gigantic, and the fact that the stable releases tend to be rock solid is little short of amazing. But if you want to install it, I recommend creating just a netinst CD and have the install process download only what you really want.