What kind of HSEB percentage is considered as good for top universties?
I believe you know that top universities do not look only academic percentage, they need several other activities like ST/ACT, Essay, ECAs, TOEFL etc. As far as HSEB Percentage, they could feel comfortable 75% or more. Over 80% is desirable. It also depends upon definition of your top universities. If you are talking about top 20 of USNEWS Ranking, they prefer more than 80%.
It really depends on your application, however, they do give more focus on the academic transcripts than other standarized tests.