Hong Kong Visa Duration

Hi I am Pakistani citizen i want to apply for Hong Kong entry permit. I am planning to visit HK as a tourist on 04 February 2018.
My question is i have been told by Cathay Pacific office that application will take 8 weeks for processing (Chinese Embassy in Pakistan does not process personal application, they only process official visits entry permit). I will submit my documents in first week of November.
What will be the duration ? If i receive my visa in first week of January will it be valid for 2 months ?? Because one month one will be expired by the time i enter HK.

I want to add here that i am submitting my application in advance because i am also planning my trips to Bangkok and Dubai simultaneously therefore i need to apply for other entry permit as well.

Thanks and Regards,
Mohammad Nabil