What does exactly the black arrow means?

[simon]

the one in the commands

[tokiopewpew]

Holding the direction button.

[simon]

is there a legend anywhere?

[Max0rz]

Not really, but there aren't that many symbols.

Black Arrow = like previously stated is holding the direction.
White Arrow = short press is sufficient
+ = pressing two buttons at the same time
White Dot = either delay the next input or it means perform the next input on hit (depends on the move)

[Gamer's Sanctum]

Originally posted by Max0rz:

Not really, but there aren't that many symbols.

Black Arrow = like previously stated is holding the direction.
White Arrow = short press is sufficient
+ = pressing two buttons at the same time
White Dot = either delay the next input or it means perform the next input on hit (depends on the move)

Oh man! Moves with white dot are very difficult for me to execute!

[My Aunt's Delicious Legs]

hold the direction
e.g. helena's hold southeast P P
then you will find the spinning hayabusa's throw and lisa's deja vu are more difficult, good luck

[Orfeo]

I've experienced it's not a simple "holding" matter. A black arrow means :
-pressing direction
-enter next input
-release input
-release direction

What I read online concur with that.