Well
the cap and glasses H region is fully INSIDE the S region. That means that S includes the H (the hats) as well as the sorts, shirts and sandals. so H is a subset of S. That would be true.
It looks to me like S stands for Summer and W stands for winter. Caps and sunglasses are just a small part of the Summer clothing set.
Note: S is not a subset of H because the S area is not inside the H area
Other examples.
A German Shepherd is a subset of all dogs. Because all German shepherds are dog.
Trees are a subset of Plants because all trees are plants.