There are two countdowns. One is for tournament (supposedly), the other for pubs. The pub one is the harder to get to.
Open up TVEd, and open the class browser. Open the GameClasses.pkg file so that it gets all the classes. Make sure non-placable classes is selected. Go Object->Actor->Info->GameInfo->GameInfo->MultiplayerGameInfo->ModeInfo->ModeDefault->ModeWhateverTheHellYouNeed
Right click and hit default properties.
Expand the roundInfoClass field, then RoundInfo, then rounds, then [0].
There it is! "countdownDuration"! The value is in seconds.
The tournament countdown time is just in the top level of the ModeWhateverTheHellYouWant fields.