Maybe there are 3 divisions with 3 division winners + 1 WC team. That's 10 regular season games and then semi-final games followed by ACC championship. That's 12 games max for the ACC champ.
...considering a 5 team home-and-home schedule. Adding ND creates 15 teams and enables 5 home-and-home series.
https://247sports.com/Article/ACC-considering-a-five-team-home-and-home-schedule-for-2020-college-football-season--149028395/