What are my options if H1b is approved only for four months?

I got h1b approval notice on August 11 2016 with duration starting from Oct 1 2016 to Jan 31 2017 (just 4 month)

Due to high volume the consulate has noted 15 weeks of wait time for stamping and my employer says we need two months prior to expiry for stamping. What should I do? Is there a way to change the date or extend before traveling?

In my i797 filing document the end date is mentioned as 06/15/2019.I am not sure why they provided approval for four months. ( my employer has created service request for this issue)

Please assist.