Dear student
The nta score is based on your percentile and not your marks. Also, marks and percentile don't follow any pattern so you can't convert your nta score to your total number in exams, you can however, convert it to your rank. Use the link below to find out how.
https://engineering.careers360.com/articles/how-calculate-jee-main-rank-based-on-nta-percentile-score
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