If they are interviewing you then you are qualified for their class. If they ask you about a poor grade or score it is just to clarify that there is some circumstance that created that situation or for you to say that you learned from a mistake. Be honest above all else. They would not be interviewing you if they did not feel you could handle the work, on paper, and participate in their programs.
That being said, what you do need to do is show them that you can communicate well and that you have a personality that will fit in with their class. As hard as it is on your first interview just try to breathe and stay calm and most of all communicate. The answers don?t matter half as much as your ability to speak and relate information. Prepare by having thought over the questions all schools ask: why do you want to be a physician, why osteopathy in particular, and then why their school.
Don?t memorize some performance of a precise answer but have in mind your reasons. When you speak to the interviewer remember he is a person like you with a family and a job and he is probably there because he wants to be. The first interview is the hardest and by the second and third you should be getting through them cool as can be. Just keep in mind that you are already qualified to enter their class, congratulations, now all you need to do is speak, it is that simple.
And try to pronounce that as that and not "dat" as you spelled it, which may not look so good. =)