What does it mean that everything is thriving, full but not full?

It means that the seeds of summer crops are gradually full, but not yet mature.

Xiaoman is the eighth of the twenty-four solar terms, which indicates the appearance of summer. The seeds of summer crops such as wheat are full but immature, so it is called Xiaoman.

Solar term is a special festival to express the natural rhythm change and establish December in the trunk and branch calendars. It is a product of ancient farming civilization and a knowledge system formed by observing the movement of celestial bodies and understanding the changing laws of time, climate and phenology in a year.