The 2021 conference projections are based on the results of 100,000 season simulations. The simulations account both for error in preseason rankings and for game-by-game win/loss probabilities.
CCG% is the percent chance of reaching the conference championship game. In conferences with a single division format (Big XII, American) the sum of the CCG% equals 200%, since the top two teams will reach the championship game.
CC% is the percent chance of winning the conference outright.
For more, see the 2021 College Football Atlas, the biggest (528 pages) and most advanced college football preview in the nation.