The haiku poem had many strict rules, and because of that, it has many different layers of meaning.
Most haiku poems are about nature or the seasons.
Just like there are multiple kinds of memory, all of which affect people's lives, there are many kinds of personalities too. Personalities are connected to memories because memory affects personality.
The poem as a whole means that everything is being recorded in memory. It shows how every event is important, and how each one has a place in her mind.
A haiku poem is usually about nature, and this poem is about the natural process of memorization, instead of the author's life. It is different from the other poems in that way.
Unlike other poems that talk about specific events in her life, it talks about events themselves and how they are imprinted into her memory.