By saying “on any given day” you are suggesting it’s a different 12%. The article does confuse this by identifying cohorts that eat more beef. But it’s a tautological label based on the survey data. They identify some correlates, like being a 50 something male. But there are males who are 50 something that don’t eat any beef. They’re not included in the 12%.
The 12% is just the outcome of the sample. It doesn’t mean they’re a consistent cohort.
Example:
* on any given day x million women give birth
* there are x million women who give birth every day