That is an external pip as miss Lydia said they take a long time to hatch so be patient it can take up to 48 hours to finish
If they hatch in the evening/afternoon I leave them in the incubator over night I find that they don't fluff up until they come out, if they hatch in the morning then I...
Can you see baby moving day 16 you should see movement
I don't know about the spec but maybe @WVduckchick or @New duck mommy 2021
Also do you mean you found a wild Mallard egg and took it or you are hatching Mallard eggs
Another question do you have one egg in the incubator or more than one...