Your link is from 2019.
It states the statistics in a very confusing and convoluted way:
"In our analysis,
over half of low-wage workers have levels of education suggesting they will stay low-wage workers.
This includes 20 million workers ages 25-64 with a high school diploma or less, and
another seven million young adults 18-24 who are not in school and do not have a college degree."
So, it sounds like there are 27 million times 2 = 54 million. Yes?
27 million are transitioning out of the low wage categories. 27 million are thought by the author to be trapped in the low wage category, but 7 million of that number are are young and presumably will transition out of that category.
That leaves the 20 million folks trapped in their low wage category. 20 million of 330 million is 6% of the whole.
The wage they cite in the article is about $18,000/year in 2019 and is presumably higher right now.
The average Social Security check issued in 2021 annualized to $17,244.
https://www.bankrate.com/retirement/average-monthly-social-security-check/
It would be nice if EVERYONE earned Elon Musk type of money, but we just don't.