Question re: semi final league divisions

Are the divisions determined at random or through some seeding system? If the latter, what is the system?
1, 6, 9, 12
2, 5, 8, 11
3, 4, 7, 10?
1, 6, 9, 12
2, 5, 8, 11
3, 4, 7, 10?
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http://forum-365.strat-o-matic.com/community/
http://forum-365.strat-o-matic.com/community/viewtopic.php?f=8&t=637288