I call BS. This research paper is being used to generate clickbait headlines like "Scientists Say There Are at Least 36 Intelligent Civilizations in Our Milky Way Galaxy"
bullfluff!
I can't see behind the paywall but they seem to be inferring that they know the upper and lower limits of their 'Astrobiological Copernican Weak and Strong conditions'
They're going to make predictions and form a hypothesis based on a sample size of one?
They admit exactly that shortcoming in their own words:
"These assumptions are based on the one situation in which intelligent, communicative life is known to exist—on our own planet"
Better to just admit "i dunno" than to just pull stuff out of yer ass

There are far better discussions on the subject

Like here:
https://youtu.be/AC-6okOWXLs

and here:
https://youtu.be/JjVYYgUxb_0

and
B⭕NUS