That, I am not sure. I have zero knowledge in programming indicators. Volume as well, for VSA, is a relative thing, so I am not sure if a certain figure would be a great idea. That would also be different with different brokers, as it is not Actual volume, but tick volume, which is as good as it gets (but pretty darn good anyway).
A "Climactic Volume" event could occur any time, so the climactic event, if in Asia session, could simply resemble the same volume as London session for example.
Attached below is a good example of what I mean with climactic volume in "out of hours". The idea being to also compare that volume (H1) to that of previous days as well to work out what "average" is.