Hi Syamsai,
For 123 marks, you are expected to get about 97.1- 97.9 percentile, assuming you belong to the General Category and are not Physically Challenged. You can check the score yourself on your JEE-Mains 2020 percentile predictor here:
JEE Main Rank Predictor - Know your expected IIT JEE Main 2020 Rank by ...
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