Hii aspirant
Hope you are doing well amid covid-19 pandemic
Like if you are talking about 70%  in board exams yes you can appear for JEE advanced
The criteria for JEE advanced was to secure atleast 75% in you board exams but due to prevailing covid-19 pandemic there is relaxation for this year and the board marks will not play a major role as it used to in previous years
But you must be under 250000 rank in JEE MAINS to appear for JEE advanced entrance
I'm providing you with the eligibility link for the jee advanced it will clarify all your doubts

https://www.google.nl/amp/s/engineering.careers360.com/articles/jee-advanced-eligibility-criteria/amp
Hope it helps

Hii,

Yes you are eligible to give the jee advanced paper. As the authorities has give concession for board marks eligibility this year due to covid-19 or corona virus. You are eligible for the paper. Wish you all the best for the paper. Hope you got the answer.

Regards