Thanks for responding to my questions. I have found the problem in my grade book. I think Karen Shackleford-Cesare also had the same problem as me. I will mention the reason for this issue and how did I solve.
The problem is the grades are not properly shown in the user report as per the "weights" we specify in the grade settings. It shows either as 0.0% or 100.0%. It shows incorrect grades for students.
In such situation check whether the course total is overridden for that student. In the above pictures (in this thread starting post), the total is overridden.
The solution is removing the override option of course total at the "single grade view for the student" which can get from grader report by clicking the relevant icon next to the selected student next to name column.