H4 visa - Spouse H1 valid only till October 2019

I have an H4 visa appointment on August 5th , my spouse is in USA and his I94 is valid till October 2019.
What can be the best answer if the Visa officer asks me why do you want to go only for 2 months as the Primary Applicant’s i94 is only till october?
Please note : my spouse’s I140 is approved and the employer is also getting documents ready to file for ane xtension.

You already have the answer with you, just the same thing that your Spouse’s employer is planning on filing the Extension in the upcoming weeks. The only thing is they will issue you visa stamping until October 2019. You should not make up anything, should tell the facts so that you do not get into trouble.