Its important to read the bounty rules before participating in that bounty. They might have some rules that will prevent you from joining or probably not following them will lead to loss of funds at the end of the period.
Thats normal before you join, and its also normal if the manager changes the rules of the bounty, so its advisable to read every week the rules and regulations or the thread to know the changes and of course to monitor you details on the spreadsheet because there are so many scammer on one project.