Other people see the issue assigned to me, why ?

Hello,

I'm kinda new to Redmine.
I just create some project and some issue, applied some to me.
I add user as dev to the project (I'm manager+dev of this project).

My user can see the task applied to me in his "my Page" > "Issue applied to me" (he customs the page).
I would like to understand why, and to find how to hide, it please ? I want him to see only the issue applied to him.