Global Password Reuse
Setting this to Not Permitted will prevent the password generator from reusing any account or synchronized password for as long as past passwords are retained.
Per-Account Password Reuse
Setting this to Not Permitted will prevent the password generator from reusing a generated account or synchronized password for as long as past passwords are retained on a per-account basis
Past Passwords are configurable from Global Settings | Past Passwords.
The default is 5 and max value is 30.