Board Thread:Questions and Answers/@comment-82.156.232.82-20150627184823/@comment-2045890-20150715010323

Both PvE and PvP events have 5 time slices. Each PvE time slice further contains two brackets of players (easy/hard depending on your past performance), while PvP time slices seem to have only one bracket.

New brackets open up as old ones are filled. PvE brackets normally contain 1,000 players, while PvP brackets normally have 500 players. Each bracket is essentially treated as an independent event (i.e. what you called "overall event"), so players in different brackets can have very different rankings even if they have the same score.

One of the tricks to getting better placement rewards is to join an event late and try to sneak into a fresh bracket. Taking advantage of this generally requires some out-of-game communication between players however. There are, for example, threads on the official forum where people keep track of how brackets are filling up to help others get into fresh ones.