Password Expiration Warning: not entirely clear

It is not clear to me what value to enter in the 'Password Expiration Warning' field.

The description says: 'The comma separated list of days. The warning about expiration of the password will be sent out on those days before the expiration. Leaving this field empty won't send out or display any warnings.'

Maybe also add an example value to the field description.

Is a correct value 'Monday,Tuesday' ? Or do you need to enter weekday numbers, like '1,2' Or are they the day numbers in a month ? Like every 10th and 20th of a month, like '10,20' ? Or is it X days before expiration, so if your passwords are valid for 60 days and you want to sent a warning after 50 days, you would have to enter '10' ?

So just a little bit more info would clear up confusion I think.

I worked out it is the last option: X number of days before the expiration date by studying the password_policy_expiration.test file.

I would change this text:
'The comma separated list of days. The warning about expiration of the password will be sent out on those days before the expiration. Leaving this field empty won't send out or display any warnings.'

To this:
'The comma separated list of days, describing the number of how many days before the expiration date the warning mails about password expiration should be send, for example '14,7' meaning: send a warning mail two weeks and one week before password expiration date. Leaving this field empty won't send out or display any warnings.'