>the winners of all classes are assembled at the conclusion of judging and the CC and Reserve Cc are awarded
As Toolz said, with the minor addition that it is all class winners that have not been beaten in a subsequent class. We all take it for granted, but could be confusing when you're new to this strange world.
I suspect that what you're really thinking about is which class wins qualify for Crufts, rather than for the CC. The wins that qualify are 1-3 in Minor Puppy, Puppy, Junior, Post Grad, Limit and Open. Some breeds can also qualify from Yearling classes, but this won't apply to Leos.
M.