It happen again..

And it happen again. I guess i have get the highest mark for the report in the class. And it is 17.5/20, 19/20 and 19.5/20. The average mark is 18.67. Although i get high mark but what i aim for is the full mark. Feel a little of disappointment because cant get the full mark . The worst mark is the first full report.  What wrong with my first full report.Can you tell me my mistake?I purposely come ealier  to school and it was just a 10 minutes class. The lecturer should discuss where is the mark located, and he didnt do so..