Draft % sauce who can explain

Who can (or is willing) to explain the sauce for Zwift % gauge for me ? I’ve seen that it reports 0 to 200, 300 or up to 500%. First what is the upper limit & what is that telling someone ? i.e. are you really saving 500% of power output in a draft at a particular moment compared to what ? I assume the person at the front perhaps ? I do not have Sauce nor use it but am intrigued since my drafting &/or ability to ride smooth in a group stinks. (Saris H3 ) Your opinions are welcome & appreciated

It’s watts saved. (forget the %, that’s wrong, and I believe is removed from the latest version of sauce)

So is there any indication of the efficiency of the draft being used ?