US Immigration Service's reply

In addition, you should also pay attention to whether your case is approved. The timetable published by the Immigration Bureau in the middle of each month only indicates the progress of issuing the "visa number" for approved cases. Due to the limited number of green cards issued by the Immigration Bureau each year, the number of approved applicants far exceeds the number of green cards that can be issued, so the scheduling method is adopted. Among the approved applicants, the priority date is given the "visa number" (a necessary condition for visa interview or identity change, that is, a necessary condition for obtaining a green card).

Sometimes, some applicants will meet the deadline, but the case has not been approved and is still in the stage of supplementary evidence or trial. In this case, even if the schedule has arrived, it can't help them. So it should be noted that the scheduled arrival does not mean that the green card is available.