Sonos doesn’t publish those numbers, as they have little meaning in a self powered system. What you see on their sales pages at www.Sonos.com is all they publish. 

but what if someone knows? other products from other manufacturers have them, for example, I need to calculate how many subs I need for my room

and how will I know if my system is working optimally?

In any normal room you'll need just 1 sub.

If the sound you hear is good, the system is working optimally. Let your ears decide and forget about the numbers.

One could even say that people that need these specs and numbers are not the Sonos target market. While, at its best configuration, Sonos can deliver sound that is as good as what makes that deliver to such markets deliver.

Buy and set up your system. Listen for a while. If you decide you need (or might need) another Sub, buy it from Sonos. If you then find it’s not needed, Sonos offers a home trial in most regions, so just return it within the trial period for a full refund. 

What is a “normal room”, what is it?

Just try working with one Sub first. If you are not satisfied with the sound, try adding a second one. Indeed: trust your ears.

Normal room is a bit vague.

I have a Sub in a 10x10 foot room and have to keep it dialed WAY down. I’d have been better off with a mini-Sub  if they had been making them back when I was buying.

I have a Sub in an open-plan room, L shaped with vaulted ceilings, long walls are about 30, end walls about 15 feet. It seems to be plenty to fill the room with just a single step above the default volume level.

I’d guess around 700 square feet is reasonable for a single Sub given my experience. Of course proper placement figures in too and the optional second Sub can do a lot to offset poor locations, larger spaces or the desire for boosted low frequencies.