yes it takes around a month, also you can refer to the below NVC link:
https://travel.state.gov/content/travel/en/us-visas/immigrate/the-immigrant-visa-process/collect-and-submit-forms-and-documents-to-the-nvc/step-6-submit-documents-to-the-nvc.html
This link displays the current under review cases information, submitted on specific date, also I have noticed that they update this information on this link every Monday.
Here on looking this screenshot from this link, you can tell that they currently (on 9-Dec 2019) reviewing documents submitted to NVC on 21-Oct 2019.
And on coming Monday(16-Dec 2019) they will update this information again.
Once they done review your submitted documents then either they will ask for any missing/additional document(they can even say that the uploaded scanned document's quality is not good for readability) or update your case status to Document qualified.
M Naeem got a reaction from Kashan.01 in NVC Working with the U.S. Embassy ISLAMABAD to schedule an interview