Cue Problem DDJ FLX4

I am having trouble cueing up songs without them playing out over the master. I play one track using Rekordbox on the left side with the left levels up. I put another track on the right side with  the levels all the way down, and when I press play and the right cue button lights up and I press it, the sound comes out full volume over the  master, mixed with my left side track. What am I doing wrong?