You can get to this screen from my chance button or options menu.
Scores are computed as the percentage of the sum of all scores. Hence, share of each topic (viz., Physics, Chemistry and Mathematics) is 33.3% only.
Below is the table depicting how scores are graded.
|less than 10%||Poor|
|10% - 20%||Average|
|20% - 30%||Good|
|30% and above||Excellent|