Major & Minor Magical Focus - Confused!

Can anyone please explain in clearer terms, just how this virtue works!

My lack of clarity is over the application & choosing a focus; i understand about the doubling of the lower art but not much else!

Specifically the sentence "Should be smaller than a single art but may be spread over several arts"

One of my players has this & it is "Men"; does this mean casting any spells on men grants the doubling of the lower art?

Arigato in advance!

YSMV but for most interpretations, yes.

Also, any spells designed to specifically affect men will find that the lab total doubles for development.

At least that's the way I interpret it. As said, YSMV.

I think you mean: the lower art is doubled and added to the lab total rather than the lab total doubles...

Yeah, sorry. Shouldn't reply to things while trying to not remove half my skin with the razor.

Not exactly: note that the Core book example of "Men" is an example for a Corpus Focus. Such a focus applies to any Corpus spell that you cast on men. It does not apply to seducing a man through Mentem, incinerating him through Ignem, or making him invisible through Imaginem.