We send all applicants a link to take the DISC+ assessment, and In Progress means they haven't completed it yet. They'll be getting reminder emails from us over the next few days to do so.
If they still haven't taken the assessment in a week, you'll see it change to Incomplete. This may not be a serious candidate, but they'll still be able to take the assessment if they've been on vacation or busy, etc., as long as the ad is open on your dashboard.
Only spend your time with candidates who care!