for example, this student shows up as 25%, yet when I look at the report i see this, which seems to imply that was his score on his first attempt (25%), but on his last he got them all correct.

his 1st attempt did get 25% correct, but how does that help me?

I have the same question - except mine is that scores don't seem correlated to either first or last attempts. The number displayed in the score report will be a 67 for example, but the first attempt may show that the student got 13/18 correct (hence a 72%) and the last attempt shows 16/18 correct (for 89%)  I have no idea why it shows a score of 67 in the score report.

Anyone have suggestions here?

I'm also trying to figure this out (retake scores not counting) and the only thing that I can figure is that maybe the retry was done after the due date.  Not really sure if this is what is happening but it is my best guess to this point.

My student's re-takes were definitely before the due date and I checked all the scores before the due date.  

I can't make any sense of the 67% as a score report in any case, based on what I see...

I'm having this same issue.  I'm following this thread in hopes that someone will have the answer.  

same here

No one every responded and I am having the same problem.
I opened their first attempt and it says he did 27 questions BUT it was a 9 question test!! How am I supposed to figure out his first score?

This is what I have figured out, I think! There are two types of attempts: entire exercise attempts and individual question attempts within an exercise.

For the late assignment below, the student has attempted the entire exercise 2 times.  This exercise has four questions.  The students best score on one of the two exercise attempts was 3/4 or 75% as shown.

If you click on the 75 square you can view the report shown below.  The "Attempt First" here is referring to the first attempts on individual exercise questions.  As mentioned, the exercise has four questions, labelled Q1, Q2, Q3, Q4.  The first time the student tried the individual question Q1 and Q3 they were incorrect.  Q2 and Q4 were correct.

Below we are looking at the "Attempt Last (or second)" of the individual exercise questions within the first exercise attempt.  Remember in Khan if a student gets a question wrong, they can try it again, the second attempt.  Q1, Q2, Q3, Q4 are all correct.  That means that the student got Q1 and Q3 correct on the second try of those individual questions (which were each wrong on the first try).  The score for this first attempt at the exercise would be 2/4 or 50% because the score is based on the first individual question results.  Even though with the second individual question answers they are 4/4 or 100% this does not count towards the score, only the first individual question attempts count.  After the first exercise attempt, the first screenshot would have read (entire exercise) Attempts:1 Best Score 50%.

Now the student tries the entire exercise again from the beginning with different questions.  These are Q5, Q6, Q7, Q8.  Looking at "Attempt First" we can see that the student got one incorrect (Q5) and three correct (Q6, Q7, Q8).  So the score which is based only on first attempts of individual questions is 3/4 or 75%.   On the student's second attempt on the individual question (Q5) they got the correct answer as shown in "Attempt Last (or second)" where all the four questions Q5, Q6, Q7, Q8 are green.  The student does not score 4/4 or 100% because the scores are based on the first attempts of the individual questions.

So this explains why the first screenshot shows (entire exercise) Attempts: 2 and Best Score: 75%

BTW, questions answered correctly with hints are marked as wrong.

This might help too https://khanacademy.zendesk.com/hc/en-us/articles/360028233571-What-do-First-and-Last-Attempts-mean-in-the-Exercise-Report-

Same problem on quizzes as well as exercises. Khan does not restrict to 1 attempt, and they are calculating scores incorrectly throughout on multiple attempts. One student answered 3 out of 9 questions in 5 attempts on a quiz and received a score of 60. For me, there is no 1st or last attempt shown as in the pictures in other comments from 5 years ago. I love the idea of the assignments and score tracking, but if the scores are unreliable the entire service is a worthless nightmare. This issue has not been resolved in 5 years (the age of the comments thread)?