Hello there. Hope you are doing good. I would like to tell you that there is not exact information about the number of students appeared for UPSEE 2020. However, the number of applicants this year is around 1,25,328. I am sharing a link for your reference which contains vital information related to UPSEE 2020.

https://engineering.careers360.com/articles/upsee

I hope you found this answer helpful. Good luck for your future.