from the wiki:

After six matches, the two best teams advance to the play-off. Top Eleven's ranking rule is slightly different from the UEFA Champions League rule, as the main criteria is goal difference, not match results from the teams in question. The play-off system is the same as the Cup system – you play two matches against the same opponent and the winner, in case of a tie, is decided by the “Away Goals Rule”, or by penalty kicks. The finals are played on a neutral venue which is usually the larges stadium on the server.