That's 50% _chance_ het. It either is or isn't a het but when you don't know (because it's a morph type where the hets don't show and it's too young to have breeding results) you assign a percentage to the chance that it is a het. You would know what the chance is based on the parentage. If one of the parents was a het that means it had one normal and one mutant copy of the gene in question so there was a 50% chance it passed on the mutant copy. There are even possible het pastel and spiders, it’s just that once the eggs hatch you know if they hit their chance or not because of the visible hets.
god its so damn confusing to me. i try i really try to understand it all, and im slowly getting it but SLOWLY