First, the brush size itself is stored at 4pt. But when I clicked on the second brush (size 400) and came back, The number has changed according to the size of the second brush.
The video only deals with size changes, but changes to match the brush settings you used just before, such as size/mode/invisibility/flow. Some brushes change like this, but some don't. It wasn't like this before, but it's suddenly like this.
What settings should I touch? If anyone knows the cause, please let me know.