This happens due to the way regular assignments work in Studio:
Students can complete the assignment more than once, but:
The platform will record the score from the second attempt in the MarkBook.
If the student only completes one attempt, that first result is recorded.
If the student makes more than two attempts, subsequent attempts are not recorded in the MarkBook. Instead, a message will appear on the screen indicating that the score will not be sent to the MarkBook.
This can create differences between the grade the student sees after completing their last attempt and the one recorded for them in the teacher’s system.