Tournament structure question

Is says here that the 2nd (Semifinal) stage divides the previous players (top2 from every backet) into the next 2 brackets - winners and losers. There’s 90 pooles so we have 90 players in winners and 90 in losers right? But those brackets are probably with 128 slots so who decides which players get a bye?
I want to know :frowning: