Watch every single game? Either they don't mean start to finish, they plan to let the person watch condensed games, or the person can watch multiple games at the same time. Otherwise, the sum total of MLB major league games (162 * 30 teams / 2) at 3 hours per game is roughly 304 straight days of baseball (24 hours per day).
The season is only about 180 days long. Watching only one game at a time in real time, it'd take 4 people watching baseball 10 hours per day, 7 days a week to watch all the games in around 180 days.