Change " Limit grace logins" thru iManager problem.

I wan't to change "Limit grace logins" in ConsoleOne in "Password Restrictions" from default setting of "6" to "15" for entire Tree. I used iManager and changed "Limit the number of grace logins allowed" under "Password Policy" to "15", but it seems no work. After three days, I checked it on C1, I still found that more then 80% of users' "Limit grace logins" no changed. What I did wrong? Any idea?
Thanks!