"Professor’s Office" Why does the professor say this:

Narrator: Listen to part of a conversation on campus between a student and a professor.
Professor: So what did you want to see me about Ernie?
Student: My grade, I’m not doing very well in this class.
Professor: Well, that’s not exactly true. You were doing very well until the last test.  Q1
Student: I got a D. Professor Adams, I’ve never gotten a D in my life.., before this, I mean. So
    that’s why I’m here. I hope you can give me some advice.
    Professor:Well, from my class book, I see that your attendance is excellent. No absences, so
    that’s not the problem.
Student: No, I never miss class. I’m a serious student. I just don’t know what happened on that
    test.
Professor: Did you bring it? The test?
Student: Yes, I did. Here it is. Professor:Okay. I think I remember this, but there were almost a hundred tests to grade, so let’s
    have a look at it.
Student: Thanks.
Professor: Well, Ernie... let’s see... Here it is. Yes, I do recall this test. You didn’t finish it. You  Q2
    stopped after question 15. So you had 5 questions that were counted wrong because
    they...because you didn’t complete the test.
Student: I know didn’twatch the time, and I just couldn’t believe it when you asked us to hand
    in the tests.
Professor: Yes, I see. But you did a good job on the questions that you did respond to.
Student: Professor Adams, maybe you won’t believe me, but  know the answers to the
    questions that I... that... that...
Professor: The ones that you left blank at the end.
Student: Yeah. So now I need some advice about how to bring up my grade because a D is
    going to make a big difference.
Professor: This test counts 25 percent so, uh  you’re right. It will bring it down at least a letter.  Q3
Student: I know.
Professor: Okay then. The first thing is to learn something from this. You have to find a way to
    pace yourself through tests or you’re going to have this problem again.
Student: I know, and believe me, I learned that already.
Professor: Okay. That’s good. Now, uh, what about the grade for this class?
Student: I was hoping you might give me a chance to...to maybe do an extra credit assignment.  Q4
Professor: Hummm. I don’t know about that.
Student: Oh.
Professor: But here’s what we can do. If you want to finish the test right now, and your answers are
    satisfactory, then I’ll add some points to your grade.
Student: You will? I know the answers. Really I...
Professor: ... I can’t give you full credit for your answers. That wouldn’t be fair to the other  Q5
    students, but I can add some points, and that should help you somewhat.
Student: Wow. This is great.
Professor: Okay. Just take your test over there and finish it. You had about an hour to complete 20
    questions, so, uh,...  that would be 15 minutes to finish the 5 questions you left blank.
    And Ernie... pace yourself.
Student: I will! Thanks. Thanks a lot.