Reply to NI Traktor Kontrol S4 Main Level/Audio Clipping Problem

So on the Kontrol S4 beside the main level knob there are two LED meters with CLIP written on top of them in small writing. Im just curious, the other day i was mixing and I noticed the first two small bars light up in blue under these CLIP meters. Does that mean that I'm clipping the audio and its not leveled up or ONLY when all the bars light up and the red light comes on as well ?

My master gain was at -6 db I believe and on the Traktor Software the main meter was really low , never in the "red zone". So I need to know what these things mean ... Thanks for the help everyone !