Don't know about that specific model but there are all kinds of bubble gauges out there, little ones, bigger ones, skinny, wide, tapered, etc.
Anyway, the idea would be to connect the bubble gauge to a regulator output in a proper orientation (vertical, with the regulator feeding the bottom end) then use it to potentially detect leaks.
Obviously if one has a keg being brought up to carbonation level there will be gas flowing so setup and interpretation would be important. But let's say one has four fully carb'd kegs on a manifold and yet there's a stream of bubbles. One could fathom there is a leak somewhere, so shutting off manifold valves to isolate the leaky run would be facilitated by the gauge. Once the leaky run is identified one could disconnect the gas QD from the keg and see if the leak ceases, which would finger the keg. Etc, etc...
Cheers!