Thank you my friend for all of this information. I have been able to determine that it is a Mallard duckling for sure. After looking it over really well I saw that the back toenail on the right foot had been removed. By law hatcheries have to do that on Mallards so that they can be proved that they are not a wild duckling as it is illegal to have them. I think it is just a plain Mallard duckling which is fine. It can run really fast but does not stand upright like it's little friend in with it the Fawn and White Runner duckling. It's hard to tell since it is only a week old for sure and I am not sure they would take the toenail off of a Runner Duckling Mallard. I didn't think to check the missing toenail until yesterday as my other two Mallards from Metzer Farms had theirs missing when I got them and it said online that was why.Are you meaning mallard coring on a runner duck? here is a list of all the colors Runners come in.
https://www.waterfowl.org.uk/domestic-waterfowl/runner_duck/