Normally bees don’t have subcastes - that’s more of an ant thing. But melliferians have the intelligence to notice hey, a little more royal jelly = bigger bee, and plan ahead and decide when or if that’s useful, creating a lot more variations due to the sliding scale of nutrition.
Seizy is basically a normally sized worker - with no further conscious decision making among the nurses, she’s about how big a worker will be.
Nine is the smallest a worker can get, a larva deprived of any more nutrition won’t survive metamorphosis. When times are hard, sometimes hives will decide it’s more important to keep the population up rather than drop the birth rate to match available resources. They prefer to avoid this if possible though, since it’s risky.
El and Threeda are about as big as workers can get before they start edging into being intercaste queen-like workers. Sinking so many resources into a single worker to get them this big is a serious investment. It can be worth it though as these bigger bees are stronger and more physically imposing, making them that much better at providing protection - or at least the illusion of it.
Not all hives have these extremes, since it’s the result of a conscious manipulation of natural processes - if it never occurs to a hive that this is possible, they may only have such individuals occasionally be pure accident. Some hives reinvent this wheel over and over, relearning how to do it when it becomes relevant, then forgetting when it’s no longer immediately necessary. This results in the social meaning of large and small workers being very tied to why they happened. A historical detail that dates generations of bees to a certain time and place.
And queens of course, are the natural extreme - receiving royal jelly throughout development and into adulthood.