This year, the team WITHOUT home field advantage plays the first two games at home, so the Sox are much more likely to be home for 1 and 2 than 3 and 4.
Also, the tickets are good for the first two home games of the series, even if they do happen to be games 3 and 4. We're all just calling them games 1 and 2 because that's what they're most likely to be.