What is small kanji part that is usually placed on the left of a japanese calligraphy (shodō) work?


There are generally small kanji on a japanese calligraphy (shodo) work.
Sometimes they are written above an inkan or inkan set. What are these kanji
for? What types of information is written like this conventionally? Is this a
necessary part of a shodo work? I think they contain some meta information
about the work but I'm not sure.

Example image is below. [![small meta
kanji](https://i.stack.imgur.com/H9av6.png)](https://i.stack.imgur.com/H9av6.png)




that's a signature. (usually the name of the calligrapher)

