From my calculations
50cubic feet/min of H2 = 1415 Ltrs/min H2 @ 500watts = 0.35w/ltr
That is OU as far as energy convertion is concerned, but, moving that amount of H2 is also an item!! H2 in liquid water is a very fine bubble, the mechanics of moving that volume would mean that a vacuum is being used in the reactor or it is water mist being reacted so as it does not have to evolve through the water.
I would go for the water mist and the reactor was flushed through with N2/Ar before switching on. 500w is not a lot of power which brings me to the amperage, 100 amps+- @ 5volts. I would say the amperage was measured at the reactor and not the main input (see what I posted on the Meyer thread).
Using inductive RF with a low volt input of around 5v at the cell could devolope hundreds of amps (this works), but there claim is way beyound what I can do.
The weight of H might be because it is not H2, it could be a heavier element of H, but that would be moving into the realms of nuclear reactions

and I don't think it would

or they might start glowing in the dark.
The last para: apart, I think there is a miss understanding of numbers, somewhere

they are certainly assuming transmutation to reach those numbers, but of what? I would say certainly not the oxygen, so where has the hydrogen come from? not the water for a fact. What other molecules are they using which contain such a volume of H apart from the one litre of water???? The Oxygen, lack of, I do not have a problem with (re. SMD) it goes to oxidation of an element in an electrode and generates electrons which can be used to power part of the system "that's why there is only 500w consumed, maybe" and a good possibility to go OU on energy value
Just my musings for today
regards
Mike