50% and 66% means there is a 50% or 66% chance of the animal being het (Having a or a recessive gene eg, Albinism, Axanthicism etc... The reason the percentages vary is because they have been breed in different ways... So too get a 66% het you breed 2 animals that have the desired gene they are classed as 100% hets because they definately have the gene... Either they have been proven or have a parent that is a full albino or axanthic... So too get 66% hets you breed 2 100% hets that will produce 25% albino or axanthic and 50% that will be 100% hets and 25% that are just normal snake but dont carry the gene. And because you cant verify between the hets and the normal animals they say 66% percent het meaning there is a 66% chance the animal is het for the desired gene... Hypo is a morph or snake that has reduced black pigment too a degree... That is my understanding of these things if Im wrong please correct me im still abit of a newbie lol....