One of my friends studied at CSVTU. According to him, there are various kinds of people who check answer sheets. 

It might be a new M.Tech graduate student. An experienced professor, who could have 20–30 years of experience in education. So, definitely, you can predict the difference in marks for the same answer sheet. And, that is the reason why similar answer sheets of students get good marks while others don’t.

• Sometimes passing the exam depends on the subject, your preparation, etc.
• Theory questions are easy to get good marks, just keep your answers and diagrams neat. These papers are mostly given to experienced faculty members for checking.
• The faculties sometimes get less time to check your answer in regular exams. This is due to the abundance of answer sheets, but not enough compensation. 

This is different in this case. In backlog exams, they get time to read your answers properly because of less number of sheets to check. That sometimes is checked strictly. Thus checking papers could sometimes be done lightly or sometimes harshly.