Others replying to you are wrong in suggesting that evidence for dark matter comes only intragalactic scales. In fact, there is evidence for dark matter at the much larger scales on which galaxies and galaxy cluster clump.
From reading the article, I believe this is literally just a finding about how many galaxies into which the known amount of matter was clumped in the distant past, i.e., more galaxies with less average mass.
https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...
The average mass density of the universe is known within a few percent.
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/denpar.html
From reading the article, I believe this is literally just a finding about how many galaxies into which the known amount of matter was clumped in the distant past, i.e., more galaxies with less average mass.