That looks enough of a break for oxygen to be getting in to the egg. Waterfowl can take much longer than chicken eggs so up to 48 hours would not be unusual. This a good read on waterfowl (Says goose but most can be applied to duck too) ~ https://www.backyardchickens.com/threads/goose-incubation-hatching-guide-completed.491013/7pm was 12 hrs since the first externally pip, still hasn't made an actual hole in the shell, is that normal?