When students take an overdue assignment, it appears again on the grading screen as "partially graded". When I don't want to grade students who submitted their assignment beyond the due date, it is confusing to see it on the grading page, which after all works as a to-do list. The best thing would be to be able to decide whether you want to block access to it once it's overdue.
Here's how to disable late work from being accepted on Extempore:
https://help.extemporeapp.com/en/articles/4895092-account-preferences