Min and max say how many of each unit type you specify will be generated on that team when the AI player tries to build it. If, say, you have a team with min 3 rangers, max 5 rangers, and min 1 missile defender, max 3 missile defender, then you'll get a team with a random number of rangers between 3 and 5 and a random number of missile defenders between 1 and 3, which will then execute whichever subroutine you specify that they execute when the team is finished being created.

For example, in a General's Challenge map I'm working on for the Chinese Infantry General, a certain team, when trained, will attempt to garrison a specific pillbox when created - or, if that pillbox no longer exists, they will simply be told to hunt for enemy units. Similarly, in the map I'm working on for the Syrian general's challenge from the Global Crisis mod, a random mix of soldiers will move to a designated rally zone within the enemy base and board a Hind helicopter, which will later deploy them on the ground outside your base and tell them to begin hunting while the helicopter provides close air support for them.

Min and max are a good way to mix things up so the player doesn't always see a wave of exactly X-number of Y-units being repulsed by their perimeter defenses every thirty seconds.