above given distribution xombines for total of 360 marks. But how is that possible as jee mains is of just 300 marks.

Hello Aspirant,
See earlier JEE-Main was conducted for 360 marks but now it is conducted only for 300 marks and for your reference Exam pattern for JEE-Main 2022 for Paper 1 and Paper 2 is described below :-

Paper 1 :-
> In JEE-Main 2022, paper 1 there will be total 90 question out of which you have to attempt only 75 (25 from each section) and there will be two sections for each subject, Section-A will be of Multiple-Choice Questions (MCQs)(20 compulsory questions) and Section-B will contain Questions whose answers are to be filled in as a numerical value (10 numerical based questions out of which only 5 are compulsory to be attempted).
> In Section B, candidates have to attempt any five questions out of 10. There will be no negative marking for Section B.
> All question will be of 4 marks and there will be negative marking of (-1) on every incorrect attempt.

Paper 2 :-
In JEE-Main 2022, paper 2 there will be total 82 question out of which you have to attempt only 77 questions for 100 marks (20 questions from Mathematics section will be of MCQs and 5 questions will have answers to be filled as a numerical value out of 10. 
Second part will be for Aptitude section which will consists of 50 compulsory questions for 200 marks and in Part third there will be two questions for Drawing test comprises of 100 marks. So in total paper will be of 400 marks.
Paper 2 for B.Plan. there will be total 105 question out of which you have to attempt only 100 questions for 400 marks (20 questions from Mathematics section will be of MCQs and 5 questions will have answers to be filled as a numerical value out of 10. 
Second part will be for Aptitude section which will consists of 50 compulsory questions for 200 marks and in Part third there will be 25 questions for Planning test comprises of 100 marks. So in total paper will be of 400 marks.

For complete details about JEE-Main 2022 exam pattern kindly check out the link given below :-
https://engineering.careers360.com/articles/jee-main-exam-pattern

Some insights of JEE-Main 2022 :-
> To qualify for JEE Mains, there is no minimum aggregate percentage criteria needed but yes if you want to take admission into NITs, IIITs or CFTIs then you just need to pass class 12th. 
> Also since last year, according to New Education Policy the JEE-Main examination will be conducted in English, Hindi and other regional languages such as Bengali, Gujarati, Assamese, Kannada, Marathi, Punjabi, Tamil, Telugu, Urdu, Odia and Malayalam.

Fo all latest updates and complete details regarding JEE-Main 2022 kindly check out the link given below :-
https://engineering.careers360.com/exams/jee-main

I hope this information helps you.
Good Luck!!