What does the pokeball sign on a wild Pokemon in diamond mean?

Hi!Pokequartz001 at your service!You may remember me from other various questions.Today,im also answering the question"What does the pokeball sign on a wild Pokemon in diamond mean?"It means,you've already caught it.this means the same thing in all the other Pokemon games.P.S.:Im sorry i put the ou in the Word you in my previous question.(I cant remember my previous question)