about verification letter for csq

hello, monkey brother i have a question to ask you.
my brother has graduated from french vocational college and applied for a csq with tefaq double b2 in the mid of november .

today unfortunately he received a verification letter.

based on your client cases, approximately how long will it take to receive a new response from immigration center and does many clients of yours ended up by directly receiving a csq receipt after a verification letter within large percentage?