What do the stacks of points, which appear during a “docker compose up” run, mean?

When installing a new Docker container using docker compose up, I get a message with a stack of points inside rectangular brackets and one at the beginning of the line:

 ⠇ Image izdock/nfs-ganesha [⣿⣤⣦⣿] 41.49MB / 67.84MB Pulling

What do these points mean: ⣿⣤⣦⣿ and ?