https://www.sciencealert.com/scientists-reveal-how-many-people-youd-need-to-colonize-mars
As few as 22 people could sustain a colony of pioneers long enough to establish a human presence on Mars.
"Long enough to establish a human presence" is a very fuzzy goalpost. Very limited usefulness even as a mere operational definition.
You need a minimum of 50 to avoid inbreeding issues and 500 to minimize genetic drift in a population.
It sounds like they're just looking for enough people to build a pied a terre though.
It's not about colonization, but a initial base not collapsing within 28 years. And collapse is here defined that the population doesn't go under 10, because that is the safest lover limit to run a mars colony. It doesn't include more arrivals in that time so no extra colonists. Nor does it consider things as inbreeding.