The number of people who pass the qualifying round will be a power of 2, or thereabouts, to minimize the number of elimination rounds that will take place with an odd number of players.
All winners of the qualifying round will move on to the elimination rounds. Additionally, as many of the top-ranked losers that will boost the number of qualified players to a power of two will also move on.
As an example, let's say there were 20 total players competing in the qualifying round. 16 (the highest power of 2 less than 20) players will be permitted to move on to the elimination rounds.
Of the 20 players, 10 will win the qualifying battle, and 10 will lose. The 10 winners will move on, leaving six more players to qualify. The six top-ranked losers will qualify, and only the bottom four will be eliminated.
Note that in the case of a tie for the last qualifying spot (in the example above, a tie for 6th place among the losers of the qualifying round), then none of the players in the tie will qualify. This means that there might be fewer than 16 players who qualify for the tournament, in which case one or more of the initial elimination rounds will take place with an odd number of people. Even if this happens, however, the number of odd rounds will typically be few in number.