Hello Aspirant ,

Total marks in class 12 are counted by adding marks of all subject and percentage is also counted by adding total marks obtained  divided by total marks  , so all your subjects will be counted but most colleges conducts admission based on specific subject which is different for different courses ,

some only counts best 5 subjects , some only counts PCM(Physics , chemistry , biology) etc.You have to count percentage and marks according to college and course .

Hope this helps.