Permissions priorities between project, team, iteration types, timelines and iterations

Hello,

I'm customizing a project and i have a lot of custom permission between project , iterations and iteration types and timelines.

I want to know if there is a priority between each project area (iteration type, iteration, timeline, team area).

In fact I define a specific access permission in an iteration but not in the timeline containing it . A manager role can made a specific action "Agree" on a workitem in the iteration  and in the timeline permission he cannot. But when my workItem is planed for the iteration considered before the "Agree" Action is refused for a user who have a manager role....and if i check the permission in the timeline it's OK....

What's wrong in my configuration?

Thank you,

Thomas