BTW, To clarify, 50% possible het means that each individual baby has a 50% chance of being het Ultra or Amel.
Got to thinking and figured that a further clarification would be useful in this case.
Normally, 50% poss. het, is just that ... meaning there is a 50% chance that a baby will inherit a het gene (that a parent carries) and 50% chance that it will not.
This is because each parent carries two genes, at each locus, but each parent only throws one gene (from a pair of genes) to the baby.
Het (heterozygous) = 1 copy of a certain gene (50% chance that this gene will be thrown and 50% chance that it will be the other gene of the pair).
Homo (homozygous) = Two copies of a same gene (this certain gene will be passed, 100% of the time, since there is not another option .. both genes, of the pair, are the same).
However... In the case of Ultramels (which is what a Golddust is with the Caramel gene added), ... Ultra and Amel share the same locus (position on a chromosone) so... one or the other gene will be thrown.
This means that each individual baby ~will~ be either het Amel ~or~ het Ultra (50% chance for either/or). You just will not know which was inherited, by any individual baby, without test breeding.