It just means that when you sing, to maintain the same feeling of natural recoil inhale in the ribs/lungs and suspend that feeling while you sing, versus pushing the breath. Push all the air out, and watch how your body recoils the air in without your help, with an open throat. You basically want to sing on this feeling and NOT let it collapse. No need to inhale extra air unless you’re singing a long passage, and even then, you always have the air you need. It’s just a matter of learning how to suspend and maintain the feeling of the natural recoil of breath as you sing, versus letting it collapse/push air. In less words, with a relaxed stomach, inhale, and before you get a chance to finish inhaling, interrupt the inhale with sound. This will help you start feeling what you need to feel. The ferinelli exercise also explains these controls.