The Bracket type of User retention report shows the percent (or the number of users) who came back in a specific period.
The report supports Day 1, Day 2, Day 3, Day 4, Day 5, Day 6, Day 7- Day 13, Day 14-Day 29, Day 30 - Day 59, Day 60 -Day 89 and Day 90 -... retention. If the player returns to the game in any day inner the period, he will be counted in the appropriated column. If the player comes back in different days inner the one period, he will be counted only once.
For example, the player joined the game on 01'July. Then he played the game on 03'July and on 09'July.
Bracket retention for this case shows the data for Day 2 and Day 7 - Day 13 retention.