Sometimes you ask: In the e-mail body, how will I know or the system will knows what is the right place to place the member name or the site when we use the %s for all them (username, site, and link)? Does it have some order? How does it work?

Here is the Answer:
It is defined in the controler.php file at yoursite/com_alpharecommend. If you check the line 171 you will find the order it is defined at: $body = sprintf( $msg, $SiteName, $sender, $link) . " \n" . $custommessage;