weightage in marks in an exam is the quota assigned to a particular segemnt as this time, 40% weightage would be given to 12th marks in JEE Mains.

this means from this time on, the 12th marks would also matter in the jee mains selection and hence students need to score good marks in 12th also along with english and the fifth subject along with the rest PCM.

here, the rest 60% will be from the  JEE exam.