A2 should be 8fps, 125ms.
How does the 'Q = vA' law you mention apply, to reason on an example, to the case of A2, as a limiter to the rate?
> A2 mode which is a 1 bit mode and is a non-stable state so it will decay
It makes little sense to use A2 on a long-lasting render - nonetheless, I suppose the decay time will be relatively long (I have never notice an A2 dot change state...).
That's not 20 fps. That's A2 mode which is a 1 bit mode and is a non-stable state so it will decay. I'd recommend you read the user manual about how that works.