Changing B2 Visa Extension date in already submitted application

[ssingale]

Hello,
I have applied for B2 visa extension of my parents. I have asked for extension until November 2020. I need to change the extension date to Decmeber 2020 in current application. Is this possible to be done ? My parents have their biometric appointment scheduled later end of this month. They came to the US in December 2019.

Thanks,
Sanchit