Attack segments?

I just discovered something when I was fiddling around with the song editor, in Stepmania 5.

I just selected a bit of song, and then I pressed "A".


And then I selected that option.

And I won this.
I think that this only makes... Er...
Something to change... I DON'T KNOW, but you can change these when you select a song and you press "START" when the game tells you to do so to enter options.

I didn't want to do anything so I press "EXIT", only to get this:


I couldn't erase that, so I had to edit the .sm and the .ssc file to remove that thing.
I want to ask, what's this?
Because I want to remove that easily :P

Go to the beat where the attack starts and press enter. The second to last line says "Modify attacks at current beat". Scroll to that line, hit enter.
The attack should be there; on the right where it says modify... hit the right arrow on your keyboard once and it should say delete. Press enter.
This gets rid of the attack