Description of Options

Auth Link is valid for: The Auto Login Link will expire after the given time in hours.
Maximum Page Views: You can limit the amount of page views. This option make it possible to only view the invoice and do not make other changes. Or to leave a ticket feedback, but do not permit to make more requests.
First URL Token Parameter: You can change the GET parameter name.
With this option you can change the name of the URL. E.g.: https://my-whmcs.com/clientarea.php?MyCustomToken=....&MyCustomToken2=....
Second URL Token Parameter: Same as above
Expire all other links on click: When client opens a Auto Login Link, all other links for this client will expire.
Expire all links on password change: If the client changes his password, the Auto Login Links will expire.
Expire all links on mail change: If the client changes his mail address, the Auto Login Links will expire.
2 Factor Authentication: If the client uses 2 factor authentication, you can force him to login regulary. Otherwise, the 2 factor authentication is skipped.
Alert Boxes via Javascript: Description
Enable Opt-Out / Opt-In: Enable this option if you want to allow your clients to Opt-Out from Auto Login. The Auto Login Link will not log them in.
Opt-In / Opt-Out Field: To use the Opt-In / Opt-Out option, you need to create a new Tick Box custom field for clients. After that select the created field here.
Client must Opt-In: Choose this option if you want that clients must explicit enable the Auto Login Checkbox (your created custom field, which can be found at the client profile page).