While not very common, if you have been in the system taking training, you may occasionally find that some of the same learning activities are used across multiple courses. For example, a quiz found in one course may be also present in another course.
When multiple courses share a learning object such as a quiz, the status for that learning object persists across those courses, even though you may not have necessarily completed it inside the current course you are taking.
If your course has a "Reports and Scores" tab/page, view it - it will provide contextual data for the course you're viewing it from including completion or passing status.