[horde] Ask for help of setup Authentication page

[Jason Wang]

When I fill the setup page's Authentication Tab, I select SQL authentication & Custom parameters.
 
1) I don't know what the means of "The name of a field containing a UNIX timestamp." --> Can I only fill it with "disable"?

2) About "This is how often, in days, the user must change his or her password. When the user's password is updated, the "soft" expiration is set this many days in the future. If not provided, the user's password will not expire by default." --> Can I only let it be empty if I want it never expire?
  
3) About "The number of days in the grace period the user has to change his or her password after it has expired. If not provided, the grace period will not expire." --> Can I only let it be empty if I want it never expire?
  
Are there any reference pages? 


Thank you very much for your kind support.
  Best Regards.

Jason Wang
E-mail : wjs at sha-etech.com