Why does Late Dock always show this window on startup & how to stop it?

As the title says, every time I boot up my computer the window in the image always pops up. I usually just close it, but it'd be great if I can have it not appear at all since I have to close a bunch of other windows.

Does anyone know how to prevent it and what it is?

Also, does anyone know how to close windows on startup?

https://preview.redd.it/b5na97pspqo71.png?width=1104&format=png&auto=webp&s=92eca37cbbfbe7997a2fa601dea4bfcae772a1df