Yes you will still have the video for longer if you have that set for longer in clips and archiving, but the alert images in this case disappear after 6 days, so if you clicked on the calendar a day for last month, you will have no alert images to click to view the trigger and would have to watch the whole bvr.
The red dots simply show the days you have alert images for, which in your case is 6 days due to your settings.