@LoriSolomon-We1 - that is strange...it should give the difference of the two numbers in the fraction which would be 13. I would try clicking the link for the number of students not assessed (see image below), and manually check the scores of a few specific students that are seemingly not assessed. (To check scores if you are an admin, go to the Manage Students page and click the student name link to open the Student Report. On the Student Report, you can open a standard you think was assessed and see if the assessment is listed.)

It may have something to do with students coming in from the SIS or another set up issue. You may need to submit a ticket with the Support team who can investigate the specifics. I hope this helps! - Jen