Custom certificate (plugin)

Thank you Mark!  So how does the certificate module know how long the user has been logged in? I want my students (or at least the administrator) to be able to check their time and see if they have been in the course long enough to generate a certificate.  With courses 90 hours long, with certificates that can't be generated for 12 days, I want them to be able to verify their time.  I first had them click on their name and look at their profile for a time, but the first access....last access was a little confusing.  I didn't know for sure when they were getting logged out.   I then used the 'attendance register' because that allowed them to log time when they were reading offline.  I didn't think that the certificate's 'required time' would use it though.  Do you have a suggestion that will enable a student (or even the administrator) to check (or even tweak by the administrator) the time logged by a students so we know when the student is able to print a certificate?

I have included your code, because I thought maybe you could use it to give me a hint about where it is verifying the student's time against the required time.

/ Check if the user can view the certificate
if ($certificate->requiredtime && !has_capability('mod/certificate:manage', $context)) {
    if (certificate_get_course_time($course->id) < ($certificate->requiredtime * 60)) {
        $a = new stdClass;
        $a->requiredtime = $certificate->requiredtime;
        notice(get_string('requiredtimenotmet', 'certificate', $a), "$CFG->wwwroot/course/view.php?id=$course->id");
        die;
    }
}