Early H1-B Visa extension stamping in INDIA

Hi,

How early I can go for VISA extension stamping in INDIA. I didn’t go to India last 3 years. My last Visa stamped date on passport was Sep 30,2013.

I have got my first extension I-797 A from Sep, 2013 to Aug 2016. But that’s not stamped on my passport.

Now I have got my another extension approved I-797 B from Aug,2016 to Feb 2019.

I am planning to visit INDIA on this month. How long do I get my extension this time?

Thanks in advance…