Okta password policy username separated with special characters

Hi all,

I am checking set password methods and there is a rule that says no parts of your username should be in the password.

If I use this
email: test.ctc28282442@gmail.com
password: Atestaaa2

I got error saying that username can not be part of the password I assume username in the email is being split by “.” similar case for “-” and “_” but if I try with a “+” instead of “.” I am able to set the password.

Do you know which characters are being taking into account for splitting username?