On the about page you can read more about how they did the rankings. None of the people went to the Cal State system. But, it seems that in addition to averaging rankings from other sources (Forbes, US News & World Report, etc) they used student reviews from various websites (Cappex, Niche, etc).
It seems that they have a list of about 15 different ranking lists that they pulled from other websites (US N&WR National Universities, US N&WR North, South, East, West, Mid-West Regional Universities, US N&WR Liberal Arts Colleges, Forbes, etc). They then find the average ranking for all of the lists each school appears on with all lists being weighted the same. They then give this a score of 0-100 which they call “publisher’s consensus”
They also use student reviews from various websites and give those an average score from 0-100 which they call “Student Consensus”. They then average the rankings score and the student review scores to get their “College Consensus Score” which they use for their rankings.
I find this to be a highly flawed system. Being ranked #5 on US N&WR’s National Universities list is far better than being ranked on #5 on US N&WR’s West Regional Universities list. For example, none of the UCs appear on the US N&WR West Regional Universities list because they have too many PhD programs to be ranked on that list which is supposed to be about undergraduate focused universities. By giving all of these ranking lists the same weight and not punishing schools for not appearing on some lists the “publisher’s consensus” will favor smaller programs that rank well on less competitive lists. Additionally some of the rankings they use in the average such as “Washington Monthly” which is almost entirely based off affordability and accessibility in terms of cost of attendance, number of 1st gen students, and availability of ROTC and similar programs.
Overall, I find this ranking system to be very meaningless at least from the “Publisher’s Consensus” side. CalState Stanislaus is only ranked so high on their list because it ranks high on the Washington Monthly ranking (affordable and accessible) and ranks high on US N&WR Regional Universities West, but does not appear at all on US N&WR National Universities or Forbes. Comparatively, UMass Amherst is a large enough school that it appears on many rankings (US N&WR National Universities, Forbes, Wall Street Journal, Money, and Washington Monthly) and thus will inevitably rank lower on some (which is better than not appearing at all).
I would stick to finding your rankings directly from the large publishers rather than these websites which try to synthesize rankings for you.