Latem

Hello, I am a new Mandrake user, but not new to linux. I dled the 3 ISO's and burned them. When I was installing it everything was going fine, but around 90% (or somewhere near the end) it asked for an "Installation CD 4". It also said that if I dont have it to press cancel to continue installation from there. that's what I did and installed fine and everything looks great. I am just wandering what's the 4th cd and why did it look for it. thanks, Latem