Red Squares in the FileArchive

Can you tell me what the red square means next to the play count
in the filearcive,I am using ultramixer 3 full version.

This is the sign for you as a DJ that this song has been already played in the current mixing session.

Thanks for your quick reply.
I have been using ultra mixer for a few years now & i realy
like the ultramixer 3 it is spot on & will not use any other.