When a diver says

(if I just had one breath ) air supply gives 100lit or 180lit at 200bars on surface ,

 Thanks to “Boyles law”.

Diver breathing 1.5lit/min can get 66 breath (100/1.5) on surface or 120 breaths (180/1.5) on surface ..

Bearing in mind this is an emergency unit used to surface or continue a stop or help extend breathing while entangled or trapped in a cave . So its used in shallow stops or to ascend so air expands and diver uses less and stay more approaching surface . Physics in favor of the diver ..

Most of us use breath less than 1.5lit/min.

Dive guides say It was a rescue for a diver , managed the rest of the group safely while another diver got a problem.