hey ayush,

the true fact is that students who are fail to secure a minimum score of 21(out of 70) or 33 (out of 100) tends to fail in CBSE main examination and also in the compartment exam , but if the question paper claims to be very tough then lenient marking is applied , however if students are very close to get passed and lacking of 2 or 3 marks then evaluator may try to get you passed by somehow managing your marks and providing marks on your each attempted question.

still i would suggest do not rely on these things , prepare well

hope this helps!