Dear student,

Generally, the top 20 percentile is released after the jee advanced result comes out. But the information is not yet disclosed.
Maybe it is possible that the top 20 percentile is disclosed or not, in any way the information has not been released.

So, you can get a idea of top 20 percentile of bseb 2020 by the help of following previous year's top 2020 percentile :-

General - 346
OBC- 347
SC- 332
ST- 339

So, you can take a basic idea from this that what must be the top 20 percentile for bseb in 2020.
So, the expected range can be :-

General - 340 - 355
OBC- 330- 347
SC- 320 - 335
ST- 325 - 340